Leo Cosendai used to be an acutely anxious young man. “I couldn’t cope with taking the train,” he says. “I never felt safe.” So when he moved to London from Switzerland in 2008 to study music, he tried yoga to calm him down. But it was when he discovered gong meditation sessions, otherwise known as sound baths, that he started transforming into the smiley, serene person he is today. He was so deeply affected by the practice that he ditched his singing and composing career, invested in some gongs of his own and embarked on a mission to pass on his newfound contentment to others. “I’m not saying I’m happy all the time,” he qualifies, “but I’m comfortable with life even when it’s really uncomfortable.”

To find out exactly why banging a loud gong can have such a transformational effect on mind and body, I try out one of his sessions along with 20 other sound-bath novices. We gather on the top floor of a building near London Bridge with panoramic views of a sunset so dazzling it’s impossible not to sneak a phone snap, even though this feels unmindful and decidedly not in-the-moment. However, Cosendai remains characteristically nonjudgmental as he checks his three beautiful gongs are in order. Yoga mats are laid out with eye pillows placed at one end. Once we’re all reclined and quiet, the bright lights, noisy air conditioning and squeaky floor all feel amplified. Cosendai begins by listing these as things to simply notice and acknowledge, along with how our bodies feel on our mats, as he directs our awareness to the present moment.

The sound bath itself is topped and tailed with Cosendai’s voice accompanied by the shruti box – often used to provide a drone sound in Indian classical music. His long, soft vocal tones meld into a spot of Mongolian overtone singing, in which he appears to sing two notes at the same time: a lower tone and a melodic whistle. However, the gongs are the main event, with a side order of conch shell for added ancient Tibetan vibrations. He weaves nimbly among us with his instruments to make sure we receive all sound frequencies from all directions and distances, creating added crescendos as he gets closer. The effect is a bizarre multi-layered wall of sound which, oddly, took me out of the city and made me feel as though I was in a cave.

He bangs and rubs the gongs with big fluffy beaters, teasing out deep, reverberating, alien sounds that you feel in your bones. The overall effect is soothing, but it can sound eerie or dramatic at times, too. Like a really satisfying massage, some parts challenge your senses while others gently lull you into relaxation.

While Cosendai says sound baths were developed by westerners in the mid 20th century, we have probably always used sound for therapeutic reasons. Although there have been no studies yet measuring the effects of sound baths on the brain, there are reams of neuroscientific literature on the effects of music per se.

The effect is a bizarre wall of sound, as though I’m in a cave

“It’s an ancient tradition to use sound to alter our state of consciousness,” says Elvira Brattico, Professor at the Center for Music in the Brain at Aarhus University in Denmark, who is planning to conduct the first scientific research into the effects of sound baths on the mind. “The shamans have done it with drumming,” she says, “and to use music as a medium to deepen a meditative state is quite common in different yoga practices.” But with gong meditation, sound is offered without the physical poses – you just lie on the matt and soak it up. A method that is keeping Cosendai very busy indeed.

He is working seven days a week, from large one-off events (such as recent sessions at the Natural History Museum and London Fashion Week), to regular slots at yoga centres across London. His app Third Ear has 20,000 users and the audio book will be published early next year, recorded with “binaural” methods to render the sound in three dimensions. “Gongs produce a lot of harmonics,” says Cosendai, which is when we hear multiple tones in a single hit. “You get harmonics in everything, it’s just a question of how much of them you hear. While the piano sounds like one clear note to the human ear,” he says, “gongs are the number one harmonic-producing instruments. When you’ve got a lot of harmonics in the room, or on your headphones, they blend with each other, making baby frequencies if you like, and the more frequencies you have, the more your brain is activated in a different way.”

With these different frequencies, he says, you hear what are called binaural beats, which is “when the brain receives information from two sound frequencies that are so close to one another, the brain brings them together and hears a beat”. The thronging effect of a bell or gong sound is produced by our brains.

Brattico believes certain brain mechanisms observed in other music studies are also at play during gong meditations. One key effect, she says, is a process known as entrainment, whereby our brain waves synchronise with music. “Our neurons communicate with each other by oscillating,” says Brattico. “They fire rhythmically and there’s a particular frequency depending on how fast the oscillations are. The fastest oscillations are related to cognitive activity and motor activity, while slower ones are related to drowsiness and sleep and the deep sleep waves are very slow.” The low frequency of the gong sound, she says, may slow our neurons down towards the drowsiness and sleep zones.

The rich soundscape of the wide harmonics, adds Brattico, can lead to a positive, relaxing experience, because “it allows you to detach from the cognitive part of the brain”. During Cosendai’s session, I become completely immersed to the point that the sounds seem to temporarily overrule my migraine, both distracting me and soothing me.

The gongs create a strong response. People often cry

The effect of the gong can create a strong emotional response, says Cosendai, and it’s not unusual for people to cry. Music certainly ignites introspection, says Brattico. “It activates a group of brain regions called the default mode network (DMN) which tends to be active when we’re not concentrating on anything and letting our minds wander.” The DMN is also connected to the reward system, allowing these self-referential thoughts, or even having a good cry, to become pleasurable experiences. This would explain why I don’t want the session to end; it makes me feel good. “This combination of immersive and repetitive soundscape,” says Brattico, “might well trigger this experience of focussing on yourself. Having this in a very alert and active but relaxed state, detached from your worries and detractions, allows for a special meditative state.”

On the surface, lying there and listening may seem more passive than other meditation practices, such as transcendental meditation, which involves repeating a mantra, or mindfulness, in which focussing on breathing is a key component. “A gong bath is a lot more free in that sense,” says Cosendai, “and that’s probably why the experiences, feelings and sensations people report vary”.

While some of his clients tell Cosendai their bodies felt light, as though they were floating above the floor, for others the opposite was true, “So their bodies become heavy, almost as if they are part of the floor.” Either way, he says, gong baths shift our experience of space. “Typically the gong sounds can alter the spatial awareness of people,” he says, “which is really important, especially in cities where we’re so crowded.”

One of the reasons Cosendai also uses his voice in his sessions is because, he says, “it brings a warmer more human element. The sounds can sometimes appear a bit eerie or unfathomable, maybe the voice before and after can really help. It’s a powerful instrument.”

However, he says, the aim isn’t to merely bathe people in beautiful sounds. “It’s about what it does on the inside – what is revealed and what comes up and what you manage to feel, rather than having a sleep or feeling really relaxed. Otherwise, I’d send them to have a good back rub or something else.” He sees a sound bath as much more therapeutic. “This is why I’m doing it, he says. “It worked for me and I want to make sure it’s something available for people all over the world.”

Seven Days of Sound Meditation by Leo Cosendai (HQ Audio, £9.99) is available to pre-order on Audible

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