I have previously mentioned smart playlists that can be used to get a better selection of music. (1, 2) The one problem is that these are mainly based off the user ratings for tracks. It is pretty hard to just listen to just one type/mood from your favorite music.
Tangerine looks like it solves this problem. When you first launch it starts scanning through your iTunes library to calculate the beats per minute and the Beat Intensity for each track. (There is an option to save this information back to iTunes.
Once that process is done, you can create playlists based on this information. Also Tangerine can distribute the tracks through out the playlist to hopefully create a cohesive playback experience. These playlists can also be saved to iTunes, so you can sync them with your iPod.
I am very interested in seeing how will this works, as I am sometimes disappointed in the collection of tracks in my smart playlists. I am hoping that the playlists will be good so I can listen to this while walking to and from the train. I haven't tested the results yet, since I want my whole library to be analyzed.
[via The Apple Blog]