Piano Transcriber is an iOS app that given an audio file with piano music will generate midi events corresponding to what is being played. The app looks like this:
Piano Transcriber is fully open source, and all processing is happening on the device itself, and nothing is being sent to a remote server.
The model powering Piano Transcriber can be found at audio-to-midi.
In order to build Piano Transcriber, it needs a framework produced by the audio-to-midi project, to get the actual midi events form the model output. Currently this is palces in this repository in the model_utils folder as a static build. If you want to modify this logic, the code is found at the Rust plugins for audio-to-midi.
For this app, I used the Yamaha-Grand-Lite-SF-v1.1 Piano samples from Soundfonts 4U.