Create a (nearly) seamless playlist between (almost) any two artists
Boil the Frog lets you create a playlist of tracks that gradually takes you from one music style to another. It's like the proverbial frog in the pot of water. If you heat up the pot slowly enough, the frog will never notice that he's being made into a stew and jump out of the pot. With a Boil the frog playlist you can do the same, but with music. You can generate a playlist that will take the listener from one style of music to the other, without the listener ever noticing that they are being made into a stew.
To create a Boil the Frog playlist, just type in the names of two artists and a playlist will be generated that takes you gradually, step by step, from the first artist to the second artist. You can click on any track to hear the track. Click on the first track to hear the whole playlist. If you don't like a particular artist you can route around that particular artist by clicking the 'bypass' button. The 'New Track' button will select a different track for an artist.
Boil the Frog plays 30 second versions of your tracks. When you find a playlist you like you can save it to Spotify to listen to the full-length versions.
To create this app, Spotify artist similarity info is used to build an artist similarity graph of about 100,000 of the most popular artists. Each artist in the graph is connected to it's most similar neighbors according to the Spotify's artist similarity algorithm.
When a playlist between two artists is created, the graph is used to find the path between the two artists. The path isn't necessarily the shortest path through the graph. Instead, priority is given to paths that travel through artists of similar popularity. If you start and end with a popular artist, you are more likely to find a path that takes you though other popular artists, and if you start with a long-tail artist you will likely find a path through other long-tail artists.
Once the path of artists is found, we need to select the best tracks for the playlist. To do this, we pick a well-known track for each artist that minimizes the difference in energy between this track, the previous track and the next track.
Once we have selected the best tracks, we build a playlist using Spotify's nifty web api.