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:

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:

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:

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.

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.