Huh! I also asked for something weird (Frank Zappa + Animal Collective) and got Foo Fighters. I wonder if there's some vector math going on that makes Foo Fighters crop up if the input songs are too orthogonal.
We are essentially trying to draw a line between the embeddings of the two songs and find "close" songs to points along that line. This should give us a somewhat smooth transition - at least that's the hope.
I suspect some of it may be that we are using a euclidean line through the vector space, but using cosine distance for similarity. We're still trying to get the hang of using the vectors to build a smooth transition between songs.
We are also tuning our model and training variables, as well as pulling in more playlists, which should help (I hope).