Transform MIDI songs to create mathematical remixes. Inspired by Andrew Huang's #MidiFlip "challenge".

MidiFlip can be used to simply flip notes around, inverting all the pitches, but it also gives you raw control over the notes in a simple way so you can make arbitrary remappings.

Try MidiFlip online. You can batch convert files and download the results as a zip file. (The files are not uploaded to a server.)

The web interface supports everything the CLI does (and actually more at the moment).

It would be good to be able to look at the original song as a whole in order to transpose notes back to reasonable ranges like Automatic MIDI Inverter does, or do fancier stuff like finding the scale used and mapping it to another. (You can only look at and change a single note at a time with the current API.)

MidiFlip could also let you deal in time, reversing a song or changing the tempo, altering the duration of notes, humanizing or quantizing, stuff like that.

It would probably make sense to have two levels of configuration, one where you just define a mapping, and that could be visualized, and one where you just write code to modify the MIDI. Either way the results could be visualized, with an embedded MIDI player.

Could handle inverting pitch bends and portamenti like AutoMIDIFlip does. This would be optional, since you can specify transformations such as simple transpositions.

Install Node.js if you haven't already. Then open a terminal/command prompt and run npm install midiflip -g

You should now have access to the midiflip command.

Go to where you have some MIDI files stored, such as your music folder, i.e. on Windows cd %UserProfile%\Music and on probably most other operating systems, just cd ~/Music

midiflip -i "midis/Danger.mid" -o "transformed/Danger.mid"

midiflip -i "midis/**/*.mid" -o "transformed/"

This uses glob. ** means zero or more (sub)directories, so this will match e.g. midis/1.mid as well as midis/Avgvst/FreeRide.mid. It will output the transformed files to the given output directory, creating matching subdirectories, but stripping off anything before the first *, so you'll get e.g. transformed/Avgvst/FreeRide.mid rather than transformed/midis/Avgvst/FreeRide.mid

Add -p or --percussion to apply the same transformation to percussion as to other notes, which doesn't make the semantic sense that applying it to pitch does.

Copyright 2017 Isaiah Odhner

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