One of the ways that Music 2.0 has changed how we think about music is that there is so much interesting data available about how people are listening to music. Sites like Last.fm automatically track all sorts of interesting data that just was not available before. Forty years ago, a music label like Capitol would know how many copies the album Abbey Road sold in the U.S., but the label wouldn’t know how many times people actually listened to the album. Today, however, our iPods and desktop music players keep careful track of how many times we play each song, album and artist – giving us a whole new way to look at artist popularity. It’s not just sales figures anymore, its how often are people actually listening to an artist. If you go to Last.fm you can see that The Beatles have over 1.75 million listeners and 168 million plays. It makes it easy for us to see how popular the Beatles are compared to another band (the monkees, for instance have 2.5m plays and 285K listeners).

With all of this new data available, there are some new ways we can look at artists. Instead of just looking at artists in terms of popularity and sales rank, I think it is interesting to see which artists generate the most passionate listeners. These are artists that dominate the playlists of their fans. I think this ‘passion index’ may be an interesting metric to use to help people explore for and discovery music. Artists that attract passionate fans may be longer lived and worth a listeners investment in time and money.

How can we calculate a passion index? There are probably a number of indicators: the number of edits to the bands wikipedia page, the average distance a fan travels to attend a show by the artist, the number of fan sites for an artist. All of these may be a bit difficult to collect, especially for a large set of artists. One simple passion metric is just the average number of artist plays per listener. Presumably if an artist’s listeners are playing an artist’s songs more than average they are more passionate about the artist. One thing that I like about this approach to the passion index is that it is extremely easy to calculate – just divide the total artist plays by the total number of artist listeners and you have the passion index. Yes, there are many confounding factors – for instance, artists with longer songs are penalized – still I think it is a pretty good measure.

I calculated the passion index for a large collection of artists. I started with about a million artists (it is really nice to have all this data at the Echo Nest;), and filtered these down to the 50K most popular artists. I plotted the number of artist plays vs. the number of artist listeners for each of the 50 K listeners. The plot shows that most artists fall into the central band (normal passion), but some (the green points) are high passion artists and some (the blue points) are low passion artists.

For the 50K artists, the average track plays per artist/listener is just 11 plays (with a std deviation of about 11.5). Considering that there are a substantial number of artists in my iTunes collection that I’ve played only once, this seems pretty resaonable.

So who are the artists with the highest passion index? Here are the top ten:

Passion Listeners Plays Artist 332 4065 1352719 上海アリス幻樂団 292 10374 3032373 Belo 245 3147 773959 Petos 241 2829 683191 Reilukerho 208 4887 1020538 Sound Horizon 190 24422 4652968 동방신기 185 9133 1691866 岡崎律子 175 9171 1611106 Kollegah 173 17279 3004410 Super Junior 170 62592 10662940 Böhse Onkelz

I didn’t recognize any of these artists (and I’m not even sure if 上海アリス幻樂団 is really an artist – according to the Japanese wikipedia it is a fan club in Japan to produce a music game coterie – whatever that means). Belo is a Brazilian pop artist that does indeed seem to have some rather passionate fans.

It is not surprising that it is hard for popular artists to rank at the very top of the passion index. Popular artists are exposed to many, many listeners which can easily reduce the passion index. Here are the top passion-ranked artists drawn from the top-1000 most popular artists:

Passion Listeners Plays Artist 115 527653 60978053 In Flames 95 1748159 167765187 The Beatles 79 2140659 170106143 Radiohead 78 282308 22071498 Die Ärzte 75 269052 20293399 Mindless Self Indulgence 75 691100 52217023 Nightwish 74 332658 24645786 Porcupine Tree 74 1056834 79135038 Nine Inch Nails 72 384574 27901385 Opeth 70 601587 42563097 Rise Against 69 357317 24911669 Sonata Arctica 69 1364096 95399150 Metallica 66 460518 30625121 Children of Bodom 66 619396 41440369 Paramore 65 504464 33271871 Dream Theater 65 1391809 90888046 Pink Floyd 64 540184 34635084 Brand New 62 862468 54094977 Iron Maiden 62 1681914 105935202 Muse 61 381942 23478290 Beirut

I find it interesting to see all of the heavy metal bands in the top 20. Metal fans are indeed true fans.

Going to the other end of passion, we find the 20 popular artists that have the least passionate fans:

Passion Listeners Plays Artist 6 270692 1767977 Julie London 6 284087 1964292 Smoke City 6 294100 1784358 Dinah Washington 6 295200 1799303 The Bangles 6 295990 1832771 Donna Summer 6 306018 1905285 Bonnie Tyler 6 307407 2123599 Buffalo Springfield 6 311543 2085085 Franz Schubert 6 312078 1909769 The Hollies 6 313732 2190008 Tom Jones 6 325454 2025366 Eric Prydz 6 331837 2259892 Sarah Vaughan 6 332072 2016898 Soft Cell 6 407622 2622570 Steppenwolf 5 275770 1605268 Diana Ross 5 281037 1615125 Isaac Hayes 5 282095 1685959 The Isley Brothers 5 283467 1666824 Survivor 5 311867 1694947 Peggy Lee 5 333437 1925611 Wham! 5 388183 2244878 Kool & The Gang

I guess people are not too passionate about Soft Cell.

Here’s a passion chart for the top 100 most popular artists. Even the artists at the bottom of this chart are way above average on the passion index.

Passion Listeners Plays Artist 95 1748159 167765187 The Beatles 79 2140659 170106143 Radiohead 74 1056834 79135038 Nine Inch Nails 69 1364096 95399150 Metallica 65 1391809 90888046 Pink Floyd 62 1681914 105935202 Muse 61 1397442 85685015 System of a Down 61 1403951 86849524 Linkin Park 60 1346298 81762621 Death Cab for Cutie 57 1060269 61127025 Fall Out Boy 56 1155877 65324424 Arctic Monkeys 55 1897332 104932225 Red Hot Chili Peppers 54 950416 52019102 My Chemical Romance 50 1131952 56622835 blink-182 49 2313815 115653456 Coldplay 48 964970 47102550 Sigur Rós 48 1108397 53260614 Modest Mouse 48 1350931 65865988 Placebo 47 1129004 53771343 Jack Johnson 44 1297020 57111763 Led Zeppelin 43 1011131 43930085 Kings of Leon 42 947904 39970477 Marilyn Manson 42 1065375 45459226 Britney Spears 42 1246213 52656343 Incubus 42 1256717 53610102 Bob Dylan 41 1527721 62654675 Green Day 41 1881718 78473290 The Killers 40 1023666 41288978 Queens of the Stone Age 40 1057539 42472755 Kanye West 40 1108044 44845176 Interpol 40 1247838 49914554 Depeche Mode 40 1318140 53594021 Bloc Party 39 1266502 49492511 The White Stripes 38 1048025 40174997 Evanescence 38 1091324 42195854 Pearl Jam 38 1734180 67541885 Nirvana 37 978342 36561552 The Kooks 37 1097968 41046538 The Shins 37 1114190 42051787 The Offspring 37 1379096 51313607 The Cure 37 1566660 58923515 Foo Fighters 36 1326946 48738588 The Smashing Pumpkins 35 1091278 39194471 Björk 35 1271334 45619688 The Strokes 34 955876 33376744 Jimmy Eat World 34 1251461 42949597 Daft Punk 33 989230 33257150 Pixies 33 1012060 34225186 Eminem 33 1051836 35529878 Avril Lavigne 33 1110087 36785736 Johnny Cash 33 1121138 37645208 AC/DC 33 1161536 38615571 Air 32 961327 31286528 The Prodigy 32 1038491 33270172 Amy Winehouse 32 1410438 45614720 David Bowie 32 1641475 52612972 Oasis 32 1693023 54971351 U2 31 1258854 39598249 Madonna 31 1622198 51669720 Queen 30 1032223 31750683 Portishead 30 1178755 35600916 Rage Against the Machine 30 1249417 38284572 The Doors 30 1393406 42717325 Beck 29 1030982 30044419 Yeah Yeah Yeahs 29 1187160 34712193 Massive Attack 29 1348662 39131095 Weezer 29 1361510 39753640 Snow Patrol 28 985715 28485679 The Postal Service 28 1045205 30105531 The Clash 28 1305984 37807059 Guns N’ Roses 28 1532003 43998517 Franz Ferdinand 27 1000950 27262441 Nickelback 27 1395278 37856776 Gorillaz 26 1503035 40161219 The Rolling Stones 25 1345571 33741254 R.E.M. 24 1311410 32588864 Moby 23 973319 22962953 Audioslave 23 976745 22557111 3 Doors Down 23 1123549 26696878 Keane 22 998933 21995497 Justin Timberlake 22 1025990 23145062 Rihanna 22 1109529 24687603 Maroon 5 22 1120968 24796436 Jimi Hendrix 22 1160410 26641513 [unknown] 21 1151225 25081110 The Who 20 1057288 22084785 The Chemical Brothers 20 1105159 22925198 Kaiser Chiefs 20 1117306 22390847 Nelly Furtado 20 1201937 25019675 Aerosmith 20 1253613 25582503 Blur 19 968885 19219364 Simon & Garfunkel 19 974687 18528890 Christina Aguilera 19 1025305 20157209 The Cranberries 19 1144816 22252304 Michael Jackson 16 996649 16234996 Black Eyed Peas 16 1019886 16618386 Eric Clapton 15 980141 15317182 The Police 15 981451 15289554 Dido 14 973520 13781896 Elton John 13 949742 12624027 The Verve

I think it would be really interesting to incorporate the passion index into a recommender, so instead of just recommending artists that are similar to artists that a listener already likes, filter the similar artists with a passion filter and offer up the artists that listeners are most passionate about. I think these recommendations would be more valuable to the listener.