OK, a couple of hours later here it is. Not pretty but functional, a page that will generate a 20 track playlist within a given tempo range from artists similar and including the chosen artist.

Give it a whirl Daniel’s Artist Tempo Spotify Playlists generator.  It wont play directly in iPhone but you can easily take the playlists to Spotify.  Thanks to www.musicmachinery.com for the inspiration and a good chunk of the code… I didnt have time to learn jQuery in an evening.

UPDATE.  Two days later, I’ve now got a home-brew app running inside Spotify itself that will generate playlists using the various EchoNest filters. It was a bit fiddly involving getting a developer license from Spotify.  I can’t share it with you except as a picture or as source code… mail me if you are interested, it’s along the lines of the linked web page above but more user friendly.

It’s been an interesting exercise, now it’s time to use it…