It seems like every heavy metal band has at least one chill-out song – from Metallica’s Nothing Else Matters to Led Zeppelin’s That’s the Way.   These tracks give some relief from the otherwise relentless pounding of the hammer of the gods.  It’d be nice to be able to collect up a bunch of these chilled-metal songs into a playlist – perfect for when your mom’s visiting (she tells me that she doesn’t like pounding metal).

ChilLed Zeppelin - Some rights (by-nc-sa) reserved by Heinrich Klaffs

To find chilled metal, we can use The Echo Nest API.  The Echo Nest has calculated a wide range of acoustic and musical attributes for millions of songs. One such attribute is energy .  We can make  a simple song/search query for heavy metal songs that have low energy.  These will be our chilled-metal songs that your mom enjoys so much.  Here’s the API query:

http://developer.echonest.com/api/v4/song/search?&style=heavy+metal&sort=energy-asc

This query searches for songs by heavy metal artists, and sorts the results in order of ascending energy (so the lowest energy tracks will be returned first).  The query does a really good job of finding chilled metal.  Here’s a sampling of the results:

Sphinx (The Guardian) by Black Sabbath

[audio http://previews.7digital.com/clips/34/645345.clip.mp3]

Sphinx (The Guardian) by Black Sabbath  – energy: 0.0003

Demon Driver reprise by Gillan

[audio http://previews.7digital.com/clips/34/4179195.clip.mp3]

Demon Drive by Gillan – energy: 0.010

The Return by Saxon

[audio http://previews.7digital.com/clips/34/5318312.clip.mp3]

The Return by Saxon – energy: 0.013

Solitude by Judas Priest

[audio http://previews.7digital.com/clips/34/3544312.clip.mp3]

Solitude by Judas Priest  – energy: 0.049

Joan of Arc by UFO

[audio http://previews.7digital.com/clips/34/7952114.clip.mp3]

Joan of Arc by UFO – Energy: 0.05

Fear by Black Label Society

[audio http://previews.7digital.com/clips/34/5768332.clip.mp3]

Fear by Black Label Society –  Energy – 0.119

You can also use the Echo Nest Playlist API to generate a chilled metal playlist.   Here’s a call to create a playlist of chilled metal in XSPF format.

http://developer.echonest.com/api/v4/playlist/static?api_key=N6E4NIOVYMTHNDM8J&style=heavy+metal&max_energy=.1&type=artist-description&bucket=id:7digital&bucket=tracks&limit=true&format=xspf

You can toss this playlist into a player like VLC or Songbird that supports XSPF and start listening to chilled metal right away (30 second samples only) like this:

% curl 'http://developer.echonest.com/api/v4/playlist/static?api_key=N6E4NIOVYMTHNDM8J\
   &style=heavy+metal&max_energy=.1\
   &type=artist-description&bucket=id:7digital&bucket=tracks&limit=true\
   &format=xspf' > chilled-metal.xspf

% open chilled-metal.xspf

There you go, you now have all the tools you need to keep your chilled metal queue filled and fresh, almost everything you need to keep your mom happy.

Thanks much to 7Digital for providing audio clips and album art.