Neptunely: procedural music from MIDI files

MIDI files often found on the internet are static and boring! I’m working on a library for procedural music that can extract features of midi files and use that to transform other midi files. The project is called neptunely (

I’ve built out the library using some of my own playing but when it comes to soloing, my touch is pretty off :upside_down_face:. I’m wondering if anyone knows where I can find some examples of dynamic (actually performed rather than keyed in) midi, or would want to collaborate with me on this?

Any genre is fine, but I’m focused on a funky/neo soul vibe at the moment


This project sounds fascinating! Can you elaborate? What types of transformation do you have in mind?

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Sure, some of the transformations that already exist in the project:

  • Applying harmony from one file to another - I use this with dynamic piano phrases to go from a static progression file to a rich piece that sounds as if it were actually played
  • harmonic extensions - not sure if this is the right term, but it’s a variation on the first. The allowed notes are the notes of a chord (supplied in the form of a progression file) minus the root and plus the extensions of a chord. This one is fun to apply to melodic information
  • applying the rhythm of one midi file to another
  • limiting notes to a range - simple but effective when used in combination with the other transformations
  • uniform stochastic variation - on a longer repeated phrase, this can introduce note drops and shifts uniformly on say the first and third bars of a midi file.

Right now, I build up “models” with folders of midi patterns and run them through specific combinations of transformations that aim to achieve a desired effect… like peaceful piano vs funky melody, rhythmic octave bass line that follows the kick drum etc.

To flesh these out and build more, I do album in a day projects which can be heard by following the link: - I define what I’m calling a meta-song which describes what can happen/which models to pull from in each section and then I generate a handful of variations and pick ones I like, render it out.


Hey everyone!

I’ve been working on Neptunely for a few years now. It’s a procedural music generation engine that works off of collections of midi data and heuristics to recombine the patterns in the data. I thought the lines community might find it interesting! Here are demos showing two hours of unedited music generated entirely by the engine.

I’m very curious to hear feedback and answer any questions! If you’d like to know when a more hands-on demo is available, you can sign up for the mailing list at :smile_cat:

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