Introduction

Parkinson’s disease (PD) is associated with movement disorders and cognitive impairment, especially in people over the age of 65 years (Kalia & Lang, 2015; Nutt, 2016). It is a progressive, degenerative, neurological condition that primarily affects the basal ganglia deep within the brain (Nutt, 2016). The loss of dopamine producing cells in the basal ganglia leads to debilitating motor and non-motor impairments and loss of function in affected individuals (Kalia & Lang, 2015; Malek et al., 2016; Morris, Iansek, McGinley, Matyas, & Huxham, 2005). PD is characterised by movement disorders such as, hypokinesia, bradykinesia, dystonia, tremor, rigidity and postural instability (Hou & Lai, 2008; Jankovic, 2008; Macphee & Stewart, 2012). Therapeutic dancing is receiving increased attention worldwide (Shanahan et al., 2016). It appears to be beneficial for health and wellbeing because it combines therapeutic and sustained exercise with social interaction and enjoyable music.

There are a range of physical treatments as well as pharmacological therapies to help people with PD to move more easily. Exercise, physical activities and physiotherapy programs aimed at improving movement, gait and balance are important to the management of the symptoms of PD (Morris, Martin, & Schenkman, 2010). Exercise is argued to play a neuroprotective role, especially in the early stages of the disease (Fisher et al., 2008). Dancing is a sociable and enjoyable form of exercise and is sometimes recommended as an adjunct to traditional physiotherapy or gym training (Westheimer et al., 2015). It has greater adherence rates for PD participants compared to routine exercises (Twyerould, 2016). Dancing is increasingly used as an exercise intervention (de Dreu, van der Wilk, Poppe, Kwakkel, & van Wegen, 2012). It incorporates the elements suggested by the European Physiotherapy Guidelines (Keus et al., 2014). The guidelines describe components that should be included in movement strategy training; 1) cueing strategies to improve gait; and 2) complex motor sequences to improve functional mobility. The main pharmaceutical treatment for PD is dopamine replacement therapy (Nutt, 2016; Trail, Protas, & Lai, 2008). Levodopa is the most effective and commonly prescribed anti-PD medication, yet the benefits begin to decline after five to eight years of continued use (Fahn, Marsden, Calne, & Goldstein, 1987).

Several different dance genres have been investigated for supporting movement for people with PD. The most frequently used are: Irish set dancing (Shanahan et al., 2014; Volpe, Signorini, Marchetto, Lynch, & Morris, 2013; Volpe et al., 2012), modern dance (Batson, 2010; Marchant, Sylvester, & Earhart, 2010) and tango dance (Hackney, 2009; Hackney & Bennett, 2014; Hackney & Earhart, 2009a, 2009b, 2010a, 2010b; Hackney, Kantorovich, & Earhart, 2007; Hackney, Kantorovich, Levin, & Earhart, 2007; Hackney & McKee, 2014; McKee & Hackney, 2013).

Duncan and Earhart (2012) compared the outcomes of one hour long, twice weekly, PD tango dancing classes to a PD control group with no intervention. The tango group improved for all of the physical measures in comparisons with the control group, which showed little change (Duncan & Earhart, 2012). Argentine tango is thought to facilitate movement because the music is engaging to listen to, and the rhythmic patterns employed facilitate the listener to move automatically then actively. The music for Argentinian tango is most commonly in duple time and less frequently in triple time (Collier & Haas, 1995). The music is typically performed by an ensemble of piano, violins and double bass, bandoneon and a male baritone singer (Halfyard, 2011). More contemporary compositions may feature female singers, usually those with a low pitched voice (Collier & Haas, 1995). The lyrics are generally about love or romance, and can be solemn in nature (Taylor, 1987). They may be sung with humour (Collier & Haas, 1995).

The current study was part of a larger project on dancing involving nine participants with mild to moderate disability, or stages one to three using the Hoehn & Yahr (1967) classification system. They were recruited from metropolitan Melbourne through community based physiotherapists, PD support groups, doctors and movement disorders clinics. The larger project examined the safety, feasibility and effects on mobility, of weekly dancing classes over eight weeks (Aguiar et al., 2016). Results from Aguiar et al’s study showed that regular participation in music cued dancing and exercises enabled people with PD to move more easily. Although Aguiar and colleagues demonstrated favourable results, their study did not clarify the extent to which therapy benefits were associated with the exercises, dance steps or music. Further, to our knowledge, analysis of the music used in PD dance classes is limited, despite the powerful effect that music can have on motor control (Blandy, Beevers, Fitzmaurice, & Morris, 2015), engagement (McNeely, Duncan, & Earhart, 2015) and social interactions (Hackney & Bennett, 2014).Therefore, the current study aimed to examine the music used in therapeutic Argentine tango dancing classes for people with idiopathic PD for commonly occurring features. We also examined whether particular pieces were considered to be more successful by physiotherapists and teachers.

Methods

Participants.

The participants in the current project were one Argentine tango dance teacher, three registered physiotherapists and a registered music therapist (the researcher) who facilitated the dance classes for Aguiar et al (2016) study. Ethics approval was gained from La Trobe University, and all participants gave their informed consent. The tango corpus used in the current study is detailed below in Table 1.

Table 1.

The tango corpus

The results for pulse clarity, brightness, tonality, and modulations are shown below in Table 2. We shall present both quantitative and qualitative data for each musical element. MATLAB® gives a result between zero and one for brightness. The greater the number, the brighter the music. The pieces were grouped by their time signature for the tempo results.

The purpose of the qualitative analyses was to understand which music was deemed to be particularly helpful; which elements of the music optimised outcomes; and to develop a greater understanding of the selection of music to facilitate therapeutic movement. A secondary thematic analysis was conducted of the teacher interview and physiotherapy questionnaires, influenced by a Grounded Theory approach (Glaser & Strauss, 1967).

To further examine the music, we conducted qualitative analysis of interviews with the dance teacher who chose the music and led the intervention, and a questionnaire answered by the four physiotherapists who were involved in the therapeutic dancing classes. An in-depth, semi-structured interview was conducted with the dance teacher. This interview involved open- ended questions to generate discussion and a detailed response from the participant, informed by Minichielloand colleagues writings (2008). A questionnaire (see Appendix) was also devised and administered to the physiotherapists to gather their perspectives on the music.

In this study, we conducted a computer based music analysis of the music recordings, and a qualitative analysis of the music by the physiotherapists and dance teacher. The computer based analysis of the music was conducted using MATLAB® software. Computer-based evaluations of music recordings, also known as digital analysis, has been used in music analysis for over a decade (Knox, Beveridge, Mitchell, & MacDonald, 2011). MATLAB® software with the addition of the MIDI and MIR toolboxes (Lartillot, Eerola, Toiviainen, & Fornari, 2008; Lartillot & Toiviainen, 2007) was chosen for our research. MATLAB® has a large number of additional toolboxes that expand its’ computational applications (Mathworks, 2010(Mathews, Clair, & Kosloski, 2001; Priest, Karageorghis, & Sharp, 2004). One of the variables was brightness. Brightness is a measure of how much energy is given to individual sound events (Long, Ma, Wan, & Zhou, 2010). A short sound event with little or no roll-off has a higher brightness result (Long et al., 2010). Examples of these are plucked (pizzicato) strings, a drum tap or a staccato chord on the piano. A lower number indicates a low brightness or a more blurred sound. The pulse clarity results are higher for pieces where the downbeat is very clear and there is minimal roll off or sound decay between notes. Tonality was also of interest because an examination of the harmonic structure of music is integral to music analysis. There is minimal published information on the effect of different modalities on people, or the effect of many modulations on human movement. Cancela (2014) conducted preliminary work on preferences for chord progressions in short melodies, created to cue movement in people with PD. Komielipoor et al (2015) showed that consonant harmonies and sounds could lead to more consistent movements than disharmonious sounds (Komeilipoor, Rodger, Craig, & Cesari, 2015).

Table 3 shows the pulse clarity results for each of the tango pieces. The pulse clarity results for the tango intervention range from 0.82 for Peligro to 0.09 for Sueno De Juventud. The average was 0.32, indicating a moderately strong pulse clarity.

Table 3.

Pulse clarity results







The pieces nominated by the physiotherapists as being the most helpful are listed in Table 4.

Table 4.

Physiotherapist’s most helpful pieces

One reason for these pieces being the most successful was that “those with a louder and stronger beat were easier to follow and to synchronise the dance steps to” (physiotherapist 1). Also, they were an “auditory cue to trigger dance movements” (physiotherapist 2).

The strength or clarity of the beat was important to the teacher. She selected music that had a stronger, more identifiable and distinct beat. Examples included La Melodia and El Abrojo.

Brightness.

The results for pulse clarity and brightness are presented in the following table.

Table 5.

Comparison of pulse clarity and brightness







Of the 15 pieces, nine had similar brightness and pulse clarity. This included four of the pieces that the physiotherapists found to be most effective: Amor Y Vals, La Melodia De Corazon, Nada mas que on Corazon and Silueta Porteña. The physiotherapists also preferred Alma, La Guinada, Sueno de Juventud and Vida Mia. These pieces had brightness results that were greater than their pulse clarity result. The average brightness result for the pieces preferred by the physiotherapists was 0.34.

Tonality.

The key signature, mode strength, modulations and note distribution from MATLAB® showed the tonality for each piece as displayed in Table 2. Physiotherapist 2 advised that the harmonies were “pleasant to the ear, harmonious, enjoyable” for El Abrojo; and “lovely to listen to, gentle, uplifting and melodic” for La Melodia De Corazon. Physiotherapist 3 was not aware of the harmonies. The physiotherapists were also asked open ended questions about what they would select and avoid when choosing music. None of them mentioned harmony or tonality. Their focus was primarily on the beat and tempo of the music, which were thought to trigger movement in people with PD (Thaut, 2013).

Lyrics.

Physiotherapist 1 had a partial understanding of the lyrics. The teacher and the remaining physiotherapists did not understand the lyrics due to their unfamiliarity with Argentine Spanish. Similarly, the researcher did not understand the lyrics. Physiotherapist 2 commented: “the singer made me and the patients feel good”. The voice arguably humanised the music. The teacher commented: “The singing is also really beautiful”.

Musical form.

The musical form was not mentioned by either the teacher or the physiotherapists. Nevertheless, both the teacher and physiotherapist 2 volunteered that the ending of the music was important. The teacher commented: “some endings in the tango music are quite tricky… it wasn’t clear, or it was too drawn out or ending very abruptly”. Physiotherapist 2 said she would ask potential dance exercise participants to listen to and use “the beginnings and end of musical phrases, to help guide their movements”.

Tempo.

When selecting the music for the dance classes, the dance teacher did not have a beats per minute (bpm) figure in mind or a range of values for the most suitable tempo. She selected the pieces based on the “feel” of the music. That is, she advised that she selected music that was “not too fast, not too slow, somewhere in the middle”.

The physiotherapists did not mention the bpm for the music. They had varied opinions about which of the music pieces were too fast, too slow or appropriate in tempo. Physiotherapist 3 commented that the range of tempos for the entire musical selection was good, “going from slow to fast and vice-versa”. Physiotherapist 2 nominated three pieces as having a good or appropriate tempos: Alma - 124 bpm, La Melodia De Corazon - 128 bpm, and Vida Mia - 124 bpm. The average tempo for these three pieces was 125.2 bpm. Physiotherapist 2 assessed Silueta Porteña - 169 bpm, and Milonga De Mis Amores - 168 bpm, as being too fast, given that people walk at between 100-120 steps per minute.

Duple time pieces.

As seen in Table 6, the tempo range for the duple time pieces was 106-186 bpm, with an average of 135 bpm. The teacher and the physiotherapists described four simple duple time pieces as either ‘most effective’ or having an appropriate tempo for PD dance classes.

Table 6.

Duple time tempo results





Table 7 shows the four pieces nominated as ‘most preferred’ by the physiotherapists for PD classes, and their bpm results.

Table 7.

Preferred pieces based on tempo





Triple time pieces.

In triple time, the first beat (downbeat) is the strongest, with the second and third lighter or less clear (Scholes & Nagley, 2011). MATLAB® gave a tempo for each downbeat in Amor Y Vals and Pedacito. The participants were instructed to step to this downbeat. MATLAB® gave Sueno De Juventud a bpm for each beat in the bar as represented in Table 8.

Table 8.

Triple time pieces





Discussion

The focus of this research was to study the music heard and experienced by the dance participants. An analysis of the structural elements of the musical pieces used in the PD dance classes showed that movement was enhanced by a mix of triple time and duple time pieces; a range of keys and modulations within each piece; tempos that ranged from 79-186 bpm; and moderate pulse clarity and brightness levels. The importance of a clear beat was a recurring theme in the responses from all the physiotherapists and the teacher. In the pieces that were perceived to be successful, the predominant reason given was that the beat was strong, predictable and clear. When the downbeat was very strong and clear, individuals could respond by synchronizing or attenuating their movements to the beat (Thaut, 2013; Wittwer, Webster, & Hill, 2013). A clearly marked upbeat prepares the listener for the downbeat, possibly leading to greater confidence and success in matching the movements to the beat (Chen, Penhune, & Zatorre, 2007). In contrast, a weak musical beat makes it difficult for the participant to

know when to place their foot, as they cannot find or feel the beat easily (Phillips-Silver, 2009).

For the current study, the researcher wanted to determine if the harmonies and harmonic structure of the music was noticed by either the teacher or the physiotherapists, and if it had any impact on participants’ movement and dancing. The teacher did not specifically mention tonality, key or modulations. The physiotherapists were asked directly about harmonies in the questionnaire. The word ‘harmonies’ was chosen as the most likely to elicit a response from the physiotherapists when their level of music education was unknown. The presence of lyrics was also of interest as it could create a dual task interference issue for PD participants (Brown, de Bruin, Doan, Suchowersky, & Hu, 2009). In other words, listening to the lyrics may have distracted participants from dancing or moving. There are conflicting opinions on the effects of multiple stimuli for Parkinson’s patients (van Wegen et al., 2006). In addition, there is little agreement as to which stimuli are most distracting and for how long (Nieuwboer et al., 2007). Some distraction can cause freezing and loss of balance (Rochester et al., 2004). The presence of lyrics did not appear to facilitate or hinder movement in this sample of people with PD.

Two musical elements of interest are tonality and musical form. The tango is written in several different keys, and modulates from those keys freely. While this may be of interest to music therapists, it was not noticed or commented on by either the physiotherapists or the dance teacher. The tempo, time signature, pulse clarity and brightness levels were all perceived to be important elements for optimising dancing performance in people with PD. The musical elements that were most successful at supporting the participants in dancing the tango were duple time signature, moderate pulse clarity, moderate brightness and a tempo range 121-124 bpm.

The teacher and physiotherapists had differing opinions as to which pieces were the most beneficial, however all wanted the music to have a clear beat that was audible throughout the music. The preferred pieces had a pulse clarity range of 0.09-0.32, with an average of 0.19. These findings are in agreement with several recent studies (Leow, Parrott, & Grahn, 2014), showing that a clearly heard and felt beat is pivotal to the success of dancing for people with PD. Furthermore, the rhythm also has to be steady. Leow et al (2014) found that music where the beat was very clear (high groove music), elicited greater synchronization of steps to the music, longer stride lengths and faster stepping in people with PD.

Music that was too fast was thought to exacerbate some movement disorders in PD, such as freezing of gait and postural instability, particularly when combined with multiple stimuli such as a teacher giving instructions and managing a partner (Pelosin et al., 2010; Rochester et al., 2004; Shanahan, Bhriain, Morris, Volpe, & Clifford, 2016). In contrast, music that is of suitable tempo may well enhance movement in people with PD (Shanahan et al., 2015). For example, Rochester (2010) recorded the preferred walking cadence in steps per minute of people with PD prior to testing their ability in dual-tasking while walking. Their results ranged from 98-106 bpm, measured while the people with PD had no auditory cues. They tested their walking with all or one of the following cues: visual, auditory, or somatosensory cues (Rochester et al., 2010).They found that walking speed and stride length improved with all forms of cueing, with dual task cueing having a significant improvement. The bpm range post intervention was reduced to 101.8-103.43. The tango dancing participants in this current research had the music as an auditory cue and their co-participants dancing could be regarded as a visual cue. Additional cues came from the teacher who cued the participants by clapping, counting out loud and demonstrating with her body. Some of the music was not perceived to be optimal. For example, Amor Y Vals, a triple time piece, had the lowest tempo mark for this group of pieces at 79 bpm given for each downbeat. From the perspective of the physiotherapists and teacher, this piece had a very fast feel, in part because the music is very busy. It could be argued that stepping at 79 bpm is too slow, and that concentrating on walking slowly was difficult and had the potential to affect balance. Stepping to each beat, at 237 bpm, would be too fast, as shown by the research on gait in PD by Morris et al (Morris et al., 2010). Another example was Pedacito De Cielo. This music employed a lot of rubato for artistic effect and had a weak pulse clarity. This led to physiotherapist 1 listing it as one of the least effective pieces, commenting that it was “too difficult to count because of the variety of music instruments and the beat was not clear enough”. Sueno De Juventudhad a tempo score of 158 bpm, making it one of the fastest pieces in the tango suite. As for Amor Y Vals, stepping for each bar at 52 bpm was too slow according to the locomotor research by Morris et al (Morris et al., 2010). In terms of stepping to each beat in a waltz pattern, 158 bpm is too fast. People cannot easily synchronise their steps to such a fast stepping rate. In people with PD, a too slow or too fast stepping rate could lead to stumbling and falls. The teacher noted that the PD participants enjoyed the change in rhythm from duple time to triple time.

There were some limitations to this study. Firstly, we did not control for PD medication, with all the participants performing the dancing classes in the on-phase of their medication cycle. Whether or not their responses to music would be different when off their Levodopa awaits confirmation in future trials. The study was also limited by a small amount of data from three clinicians and one dance teacher. To optimise the generalisability of findings it would be helpful to extend this line of enquiry to larger numbers of participants from a variety of professional and dance backgrounds.

To conclude, this trial provides preliminary evidence to suggest that well-chosen music can facilitate movement to music in some people with progressive disorders such as PD. That is, music with a clear, steady and always audible beat, in duple time, with minimal key modulations and within the 105-125 bpm tempo range appears to facilitate dancing. Further trials with larger samples and a greater range of musical choices are needed, to understand more fully which music best enables movement in people with Parkinson’s.

References

Aguiar, L., da Rocha, P., & Morris, M. E. (2016). Therapeutic Dancing for Parkinson's Disease. International Journal of Gerontology, 10(2), 64-70. doi:10.1016/j.ijge.2016.02.002

Batson, G. (2010). Feasibility of an intensive trial of modern dance for adults with Parkinson disease. Complementary Health Practice Review, 15(2), 65-83.

Blandy, L., Beevers, W., Fitzmaurice, K., & Morris, M. E. (2015). Therapuetic Argentine tango dancing for people with mild Parkinson's disease: a feasibility study. Frontiers in Neurology, 6. doi:https://doi.org/10.3389/fneur.2015.00122

Brown, L., de Bruin, N., Doan, J., Suchowersky, O., & Hu, B. (2009). Novel Challenges to Gait in Parkinson's Disease: The Effect of Concurrent Music in Single- and Dual-Task Contexts. Archives of Physical Medicine and Rehabilitation, 90(9), 1578-1583. doi:10.1016/j.apmr.2009.03.009

Chen, J., Penhune, V., & Zatorre, R. (2007). Moving on time: brain network for auditory-motor synchronization is modulated by rhythm complexity and musical training. Journal of Cognitive Neuroscience, 20(2), 226-239. doi:10.1162/jocn.2008.20018

Collier, S., & Haas, K. (1995). Tango! The dance, the song, the story. New York: Thames and Hudson.

de Dreu, M., van der Wilk, A., Poppe, E., Kwakkel, G., & van Wegen, E. (2012). Rehabilitation, exercise therapy and music in patients with Parkinson's disease: a meta-analysis of the effects of music-based movement therapy on walking ability, balance and quality of life. Parkinsonism & Related Disorders, 18 Suppl 1, S114-119. doi:10.1016/S1353-8020(11)70036-0

Duncan, R., & Earhart, G. (2012). Randomized controlled trial of community-based dancing to modify disease progression in Parkinson disease. Neurorehabilitation and Neural Repair, 26(2), 132-143. doi:10.1177/1545968311421614

Fahn, S., Marsden, C., Calne, D., & Goldstein, M. (1987). Recent Developments in Parkinson's Disease (Vol. 2). Florham Park, NJ: Macmillin Health Care

Fisher, B., Wu, A., Salem, G., Song, J., Lin, C., Yip, J., . . . Petzinger, G. (2008). The effect of exercise training in improving motor performance and corticomotor excitability in people with early Parkinson's disease. Archives of Physical Medicine and Rehabilitation, 89(7), 1221-1229. doi:10.1016/j.apmr.2008.01.013

Glaser, B., & Strauss, A. (1967). The discovery of grounded theory: Strategies for qualitative research. Chicago: Aldine.

Hackney, M., & McKee, K. (2014). Community-based adapted tango dancing for individuals with Parkinson's disease and older adults. Journal of Visualized Experiments. 94 doi:10.3791/52066

Hackney, M., & Bennett, C. (2014). Dance therapy for individuals with Parkinson's disease: improving quality of life. Journal of Parkinsonism and Restless Legs Syndrome, 2014(4), 17 - 25. doi:10.2147/jprls.s40042

Hackney, M., & Earhart, G. (2009a). Health-related quality of life and alternative forms of exercise in Parkinson disease. Parkinsonism & Related Disorders, 15(9), 644-648. doi:10.1016/j.parkreldis.2009.03.003

Hackney, M., & Earhart, G. (2009b). Short duration, intensive tango dancing for Parkinson disease: An uncontrolled pilot study. Complementary Therapies in Medicine, 17(4), 203-207. doi:10.1016/j.ctim.2008.10.005

Hackney, M., & Earhart, G. (2010a). Effects of dance on gait and balance in Parkinson's disease: a comparison of partnered and nonpartnered dance movement. Neurorehabilitation Neural Repair, 24(4), 384-392. doi:10.1177/1545968309353329

Hackney, M., & Earhart, G. (2010b). Recommendations for Implementing Tango Classes for Persons with Parkinson Disease. American Journal of Dance Therapy, 32(1), 41-52. doi:10.1007/s10465-010-9086-y

Hackney, M., Kantorovich, S., & Earhart, G. (2007). A Study on the Effects of Argentine Tango as a Form of Partnered Dance for those with Parkinson Disease and the Healthy Elderly. American Journal of Dance Therapy, 29(2), 109-127. doi:10.1007/s10465-007-9039-2

Hackney, M., Kantorovich, S., Levin, R., & Earhart, G. (2007). Effects of tango on functional mobility in Parkinson's disease: A preliminary study. Journal of Neurologic Physical Therapy, 31(4), 173-179. doi:10.1097/NPT.0b013e31815ce78b

Hackney, M., & McKee, K. (2014). Community-based adapted tango dancing for individuals with Parkinson's disease and older adults. Journal of Visualized Experiments. doi:10.3791/52066

Halfyard, J. (Ed) (2011) Oxford Companion to Music. Oxford: Oxford University Press. Retrieved from www.oxfordreference.com/10.1093/acref/9780199579037.001.0001/acref-9780199579037-e-6656

Hou, J., & Lai, E. (2008). Overview of Parkinson’s disease: clinical features, diagnosis, and management. In Trail, M. Protas, E. & Lai, E. (Eds.), Neurorehabilitation in Parkinson's Disease: An Evidence-Based Treatment Model (pp. 1 - 40). New Jersey: Slack.

Jankovic, J. (2008). Parkinson's disease: Clinical features and diagnosis. Journal of Neurology, Neurosurgery and Psychiatry, 79(4), 368-376. doi:10.1136/jnnp.2007.131045

Kalia, L., & Lang, A. (2015). Parkinson's disease. The Lancet, 386(9996), 896-912. doi:10.1016/s0140-6736(14)61393-3

Keus, S., Munneke, M., Graziano, M., Paltamaa, J., Pelosin, E., Domingos, J., . . . Rochester, L. (2014). European physiotherapy guideline for Parkinson’s disease. Retrieved from www.ParkinsonNet.info

Knox, D., Beveridge, S., Mitchell, L., & MacDonald, R. (2011). Acoustic analysis and mood classification of pain-relieving music. The Journal of the Acoustical Society of America, 130(3), 1673-1682. doi:10.1121/1.3621029

Komeilipoor, N., Rodger, M., Craig, C., & Cesari, P. (2015). (Dis-)Harmony in movement: effects of musical dissonance on movement timing and form. Experimental Brain Research, 233(5), 1585-1595. doi:10.1007/s00221-015-4233-9

Lartillot, O., Eerola, T., Toiviainen, P., & Fornari, J. (2008). Multi-Feature Modeling of Pulse Clarity: Design, Validation and Optimization. Paper presented at the ISMIR conference.

Lartillot, O., & Toiviainen, P. (2007). A Matlab Toolbox for Musical Feature Extraction From Audio. Paper presented at the International Conference on Digital Audio Effects, Bordeaux, France.

Leow, L., Parrott, T., & Grahn, J. (2014). Individual differences in beat perception affect gait responses to low- and high-groove music. Frontiers in Human Neuroscience, 8(811), 811. doi:10.3389/fnhum.2014.00811

Long, C., Ma, X., Wan, W., & Zhou, Y. (2010, 23-25 Nov. 2010). A research of objective evaluation method for audio brightness. Paper presented at the 2010 International Conference on Audio Language and Image Processing (ICALIP).

Macphee, G., & Stewart, D. (2012). Parkinson's disease - Pathology, aetiology and diagnosis. Reviews in Clinical Gerontology, 22(3), 165-178. doi:10.1101/cshperspect.a008870

Malek, N., Lawton, M., Swallow, D., Grosset, K., Marrinan, S., & Bajaj, N. (2016). Vascular disease and vascular risk factors in relation to motor features and cognition in early Parkinson's disease. . Movement Disorders, 31(10), 518-1526. doi:10.1002/mds.26698

Marchant, D., Sylvester, J., & Earhart, G. (2010). Effects of a short duration, high dose contact improvisation dance workshop on Parkinson disease: A pilot study. Complementary Therapies in Medicine, 18(5), 184-190 187p. doi:10.1016/j.ctim.2010.07.004

Mathews, R., Clair, A. A., & Kosloski, K. (2001). Keeping the beat: use of rhythmic music during exercise activities for the elderly with dementia. American Journal of Alzheimer's Disease & Other Dementias, 16(6), 377-380.

Mathworks. (2010). What is MATLAB? Retrieved October, 2014, from cimss.ssec.wisc.edu/wxwise/class/aos340/spr00/whatismatlab.htm

McKee, K., & Hackney, M. (2013). The Effects of Adapted Tango on Spatial Cognition and Disease Severity in Parkinson's Disease. Journal of Motor Behavior, 45(6), 519-529. doi:10.1080/00222895.2013.834288

McNeely, M., Duncan, R., & Earhart, G. (2015). Impacts of dance on non-motor symptoms, participation, and quality of life in Parkinson disease and healthy older adults. Maturitas, 82(4), 336-341. doi:http://dx.doi.org/10.1016/j.maturitas.2015.08.002

Minichiello, V., Aroni, R., & Hays, T. N. (2008). In-depth interviewing : principles, techniques, analysis: Sydney : Pearson Education Australia, c2008. 3rd ed.

Morris, M. E., Iansek, R., McGinley, J., Matyas, T., & Huxham, F. (2005). Three-dimensional gait biomechanics in Parkinson's disease: evidence for a centrally mediated amplitude regulation disorder. Movement Disorders, 20(1), 40-50. doi:10.1002/mds.20278

Morris, M. E., Martin, C., & Schenkman, M. (2010). Striding out with Parkinson disease: evidence-based physical therapy for gait disorders. Physical Therapy, 90(2), 280-288. doi:10.2522/ptj.20090091

Nieuwboer, A., Kwakkel, G., Rochester, L., Jones, D., van Wegen, E., Willems, A., . . . Lim, I. (2007). Cueing training in the home improves gait-related mobility in Parkinson’s disease: the RESCUE trial. Journal of Neurology, Neurosurgery & Psychiatry, 78(2), 134-140. doi:10.1136/jnnp.200X.097923

Nutt, J. (2016). Motor subtype in Parkinson's disease: Different disorders or different stages of disease? Movement Disorders, 31(7), 957-961. doi:10.1002/mds.26657

Pelosin, E., Avanzino, L., Bove, M., Stramesi, P., Nieuwboer, A., & Abbruzzese, G. (2010). Action Observation Improves Freezing of Gait in Patients With Parkinson’s Disease. Neurorehabilitation and Neural Repair, 24(8), 746-752. doi:10.1177/1545968310368685

Phillips-Silver, J. (2009). On the meaning of movement in music, development and the brain. Contemporary Music Review, 28(3), 293-314. doi:10.1080/07494460903404394

Priest, D., Karageorghis, C., & Sharp, N. (2004). The characteristics and effects of motivational music in exercise settings: the possible influence of gender, age, frequency of attendance, and time of attendance. Journal of Sports Medicine & Physical Fitness, 44(1), 77-86.

Rochester, L., Baker, K., Hetherington, V., Jones, D., Willems, A., Kwakkel, G., . . . Nieuwboer, A. (2010). Evidence for motor learning in Parkinson's disease: Acquisition, automaticity and retention of cued gait performance after training with external rhythmical cues. Brain Research, 1319, 103-111. doi:http://dx.doi.org/10.1016/j.brainres.2010.01.001

Rochester, L., Hetherington, V., Jones, D., Nieuwboer, A., Willems, A., Kwakkel, G., & Van Wegen, E. (2004). Attending to the task: Interference effects of functional tasks on walking in Parkinson’s disease and the roles of cognition, depression, fatigue, and balance1. Archives of Physical Medicine and Rehabilitation, 85(10), 1578-1585. doi:http://dx.doi.org/10.1016/j.apmr.2004.01.025

Scholes, P., & Nagley, J. (2011). Time Signature. The Oxford Companion to Music. Oxford: Oxford University Press.

Shanahan, J., Bhriain, O., Morris, M. E., Volpe, D., & Clifford, A. (2016). Irish set dancing classes for people with Parkinson’s disease: The needs of participants and dance teachers. Complementary Therapies in Medicine, 27, 12-17. doi:10.1016/j.ctim.2016.04.001

Shanahan, J., Morris, M. E., Bhriain, O., Saunders, J., & Clifford, A. (2015). Dance for people with Parkinson’s disease: What Is the evidence telling us? Archives of Physical Medicine & Rehabilitation, 96(1), 141-153 113p. doi:10.1016/j.apmr.2014.08.017

Shanahan, J., Morris, M. E., Bhriain, O., Volpe, D., Richardson, M., & Clifford, A. (2014). Is Irish set dancing feasible for people with Parkinson's disease in Ireland? Complementary therapies in clinical practice, 21(1), 1 - 5.

Taylor, J. (1987). Tango. Cultural Anthropology, 2(4), 481-493.

Thaut, M. (2013). Entrainment and the Motor System. Music Therapy Perspectives, 31(1), 31-34.

Trail, M., Protas, E., & Lai, E. (2008). Neurorehabilitation in Parkinson's disease : An evidence-based treatment model. Thorofare, NJ: SLACK.

Twyerould, R. (2016). Feasibility, Safety and Efficacy of Dance for People with Parkinson's Disease: A Pilot Study. (master's thesis). The University of Melbourne, Melbourne.

van Wegen, E., de Goede, C., Lim, I., Rietberg, M., Nieuwboer, A., Willems, A., . . . Kwakkel, G. (2006). The effect of rhythmic somatosensory cueing on gait in patients with Parkinson's disease. Journal of the Neurological Sciences, 248(1-2), 210-214. doi:10.1016/j.jns.2006.05.034

Volpe, D., Signorini, M., Marchetto, A., Lynch, T., & Morris, M. E. (2013). A comparison of Irish set dancing and exercises for people with Parkinson's disease: a phase II feasibility study. BMC Geriatr, 13, 54. doi:http://dx.doi.org/10.1186/1471-2318-13-54

Volpe, D., Signorini, M., Marchetto, A., Scutari, A., Marsala, S., Piggott, C., & Lynch, T. (2012). Irish set dance improves mobility, balance and quality of life in Parkinson's disease. Movement Disorders, 27.

Westheimer, O., McRae, C., Henchcliffe, C., Fesharaki, A., Glazman, S., Ene, H., & Bodis-Wollner, I. (2015). Dance for PD: a preliminary investigation of effects on motor function and quality of life among persons with Parkinson’s disease (PD). Journal of Neural Transmission, 122(9), 1263-1270. doi:10.1007/s00702-015-1380

Wittwer, J. E., Webster, K. E., & Hill, K. (2013). Effect of rhythmic auditory cueing on gait in people with Alzheimer disease. Archives of Physical Medicine & Rehabilitation, 94(4), 718-724. doi:10.1016/j.apmr.2012.11.009

Appendix: The physiotherapist questionnaire

Instructions and questions for the registered physiotherapists in the Tango Dance intervention

· Please listen to the music you received via the Dropbox account. As you listen, remember taking part in the tango classes and how you felt as a participant and as a physiotherapist considering tango music for exercise therapy groups.

· Section one has general questions about all the music. Section two refers to two specific songs – El Abrojo and La Melodia de Corazon. Section three asks what you would do if selecting music for exercise interventions. Most of these questions need a Yes or No response. Some ask for a detailed answer.

· Please enter your responses into the form, save, and return via email.

Section One – General questions

1. Did you enjoy the music used in the tango dance intervention?

2. Describe why you did, or did not enjoy the music.

3. What were you most aware of, in the music, while doing the tango classes?

4. Did the music support you in doing the exercises?

5. Were there some pieces that you felt were most effective?

6. Which ones were they?

7. What was it about the music that was helpful?

8. Did any of the pieces of music distract you from participating in the exercises?

9. Why? Was the music too interesting/boring/unclear?

10.Were there some pieces that you felt were least effective?

11.Which were they?

12.What was it about them that was not helpful?

13.Did the music support the Parkinson’s’ participants in doing the exercises?

14.In what way?

Section Two - Questions about “El Abrojo” and “La Melodia de Corazon”

1. Please can you listen to these two pieces before answering the questions

2. Think about the rhythm for each piece. Was it conducive to the exercise?

3. Did the music have a clear and steady beat?

4. Was it predictable?

5. Was it easy to follow?

6. Did you have a clear sense of when the next downbeat would occur?

7. Were you able to match your movements to it?

8. Think about the tempo of each piece. That is, how fast it felt to you, did it feel appropriate?

9. If it was too slow, what was the effect on you and your participation in the exercise?

10.If it was too fast, how did that affect you?

11.Was the effect of the rhythms and tempi on you any different to their effect on the participants?

12.Were the melodies repetitious and boring?

13.If not, what made the music not boring despite having heard it many times?

14.Were you aware of the harmonies?

15.If yes, what was notable about the harmonies?

16.Were you aware of the various instruments in the music?

17.Were the instruments familiar to you?

18.Which ones?

19.Were you aware of the singers in the music?

20.Could you understand the singers?

21.Did you know what the lyrics were about?

22.Did your level of awareness of the singers and the lyrics have an impact on your capacity to participate in the exercises?

Section 3 - What would you do?

1. If you were choosing music for an exercise intervention, what would you want from the music?

2. What would you prioritise in choosing music – melody, rhythm, tempo, musical tastes of your participants?

3. How important is it that you enjoy the music too?

4. What musical features would you avoid?

5. What would you ask your participants to listen to, and use in the music, to aid their completion of the exercises?

6. Is there anything else you would like to add?

Thank you for taking part