Well, it could be alleviated if you put tags on your songs (or if there was a central database that tagged songs). You're mostly looking for frequency matches. Or you might have a "same but different" flag that looks for songs with words in common, but also words in opposite in common. So a sad love song is followed by a happy love song.

It's not going to be DJ-perfect where one song immediately riffs into the next, but it would seriously up the odds.

later
Tom