Lo-Fi Piano was originally a standalone app I coded while on spring break.
I recorded the samples via Cassette Tapes using my synths from the 80s (DX7, CZ-101, SK-1, VSS-30, etc):
https://soundcloud.com/lo-fipiano/free-sample-download-made-using-lo-fi-piano-81-bpm
After release, I was alerted via email about a discussion on an "Audiobus" forum:
https://forum.audiob.us/discussion/38350/lo-fi-piano-made-with-audiokit
This prompted me to integrate Inter-App Audio + use the SDK for Audiobus 3:
I also promised "AUv3" support was on the horizon.
AUv3 support was released January 2021.
Lo-Fi Piano is written in Swift.