The Radio DGCI blues night inspired me to try to compose a blues song. My indifferently successful effort is here. It sounds OK, and it follows the usual 12-bar blues progression, but it just doesn't sound like blues. Well, maybe elevator blues.
I know some of the reasons it doesn't sound authentic. Partly it's because it doesn't have any of the blues effects in it: vibrato, tremolo, shaking, flattening, and other things. Partly it's because it's in D-Major. A lot of modern blues is in major keys, but it just doesn't sound as blue as the minor keys a lot of old blues was done in. And part of it is that I just don't quite have the structure down.
Anyway, it's in a MIDI file, so you can open it up and play with it if you want. There's a great free program called Anvil Studio that will let you do this. I'm actually fairly pleased with the rhythm and bass tracks.