Midi questions:
Midi is a serial connection and there exists a standard for sending it over TRS.
1. Do any phones support sending MIDI over the headphone jack or via a standard USB C to Headphone adaptor?
2. I assume midi over Bluetooth or midi over WiFi have some sort of documentation?
3. Is there an android app that will send midi in real time over the headphone jack or over Bluetooth or over WiFi (that I could use to play a busking organ)?
4. Can a phone with USB C be a usb host for a midi device, like can I plug my phone into a drum machine and output note-ons?