12-bar blues midi generator?

[40oz]

Just about all of Doom's IWAD music uses a formulaic 12-bar blues progression. I've observed a lot of MIDI tracking software has a function to transpose parts of a track to different octaves.

For someone like me who is kind of an idiot at making music, how likely would it be for someone with some programming knowledge to create an application where you can feed it a short guitar riff or something, and it automatically spits out a full length 1-3 minutes long midi in the style of something Bobby Prince might have made for Doom?

[Maes]

Sounds like a foray into the wonderful music of avant-garde aleatoric music.

[Fonze]

With midi, it's almost just easier to give it what you want it to play, then copy+paste what you want repeated throughout. Most midi writing software is easy to use and combining that copy+paste along with a built-in transposer will make your life really easy. On the flip side, if you don't have a built in transposer, it's easy to figure out by hand, just move everything up or down by the same amount, within the same key, that's important. Blues goes from the root chord to the 4th, back to the first, then 5th, 4th, 1st, turnaround.

The great thing about midi is you don't need to be very musically inclined, just find yourself a reliable, user-friendly application.

[Jimmy]

Maes said:

Sounds like a foray into the wonderful music of avant-garde aleatoric music.

Not really. In the case of aleatoric music, the piece is "composed" during performance, as in, strung together in snippets in an order determined by either a computer system, randomness such as dice rolls (Mozart's dice game is a fine example of this), or by the performer's own inclination.

To expand on what Fonze said, the 12-bar progression goes thusly:

Bar 1: Home key
Bar 3: Key perfect fourth above (transpose up 5 semitones, or 3 diatonic tones)
Bar 5: Home key
Bar 7: Key perfect fifth above (transpose up 7 semitones, or 4 diatonic tones)
Bar 9: Key perfect fourth above (transpose up 7 semitones, or 4 diatonic tones) (or transpose previous two-bar passage down 2 semitones, or 1 tone)
Bar 11: Home key

For the material itself, you probably only need the original melody outlined in bars 1-2. The track will end up being pretty diverse melodically and harmonically even if it doesn't change, so it kind of fools the listener in a subtle way.

[kb1]

Check out cgMusic.

[Mr. Freeze]

Guitar Pro has a nifty "Transpose" option to change bars, sections, or even whole songs.

[yakfak]

there's an app called Band in a Box which would do exactly this - play back chord sequences of your choice in various preset accompanying styles, so there'll be blues in there but also funk, electro-pop and probably some hilariously embarrasing attempts at metal. if you can make the program export a MIDI like that as a starting point then you could definitely get at the innards afterwards and tweak it to your liking

on the other hand, it wouldn't be much harder than that to learn how to play music with a MIDI keybaord of your own :))) the difficulty of music's basics is woefully overstated to the point where we praise Coldplay just for being able to stand upright

[jute]

I agree that Band in a Box is the perfect program for this. Twelve-Bar Blues MIDI Generator could be an alternate title for that software.

Jimmy said:

Not really. In the case of aleatoric music, the piece is "composed" during performance

Aleatoric or indeterminate music can be indeterminate in composition but not performance, indeterminate in performance but not composition, or indeterminate in both respects. The Wikipedia article Maes linked explains this.