In the Superstitious Blues liner notes Country Joe says:

Blues for Michael is just a blues. I wanted to write the simplest, easiest song - when you're young, you want to write the most difficult forms because you want to prove you can do it. But sometimes doing the simple is really hard. This one goes back to Country Joe and the Fish stuff, the really slow simple stuff we did. The chords are simple, the lyrics are simple, it means exactly what it says And I hoped Jerry would play this song with me because we both knew Michael Bloomfield, we both know how easy it is to disappear, to die. It's real sentimental - Jerry Garcia and Country Joe, singing about Michael Bloomfield, a very famous blues musician with a drug problem who died under mysterious circumstances about ten years ago. Sometimes a song has to be really personal, about your real life. This song is about me and how I feel about the fact that this friend of mine is gone.