MidiFlip

Transform MIDI songs to create mathematical remixes. Made for/inspired by Andrew Huang's #MidiFlip "challenge".

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

You'll be able to batch convert a bunch of files by specifying a glob on the CLI.

Limitations

• Percussion via the drum kit instruments of General MIDI Level 2 gets mangled regardless of the --percussion option. Only channel 10 (which is reserved for percussion) is regarded as percussion for now.

• You can't transpose notes back to reasonable ranges by looking at the original ranges, you only get a single note at a time to look at and change.

• MidiFlip doesn't deal with time at all, so it doesn't let you reverse a MIDI or change the duration of notes or the tempo. That would be a bit more complicated than just updating pitches. But just updating pitches was pretty easy, so...

• I haven't made it into a web app just yet :)

CLI Usage

Install Node.js if you haven't already. Then open a terminal/command prompt and enter 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

Flip a single file:

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

Flip a bunch of files:

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

Mess with percussion

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

License (MIT)

Copyright 2017 Isaiah Odhner

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.