Android has supported MIDI since version 6.0 (Marshmallow). Really, MIDI is the best way to control Plausible Software instruments on Android. The on-screen keyboard is fun and useful while programming sounds, but for a genuine performance, an external MIDI controller is a must.
Connecting A USB or 5-pin DIN MIDI Controller.
There are several tradeoffs that have to be made when deciding what sort of MIDI controller you will use.
5-pin DIN MIDI
This is the original MIDI cable connector. Android devices do not have these connectors. If your controller only has this interface you will need either a USB Audio Interface with 5-pin DIN MIDI or a 5-pin DIN MIDI to USB adapter.
USB MIDI
A USB midi controller can be connected directly to the Android device’s USB jack if audio output is to be had from the internal speakers (probably not) or an analog headset jack. For high-quality audio output though, you will probably use a USB Audio interface with MIDI connections.
The USB “On The Go” adapter.
By default, the USB connection on an Android device operates in “Peripheral” mode. This is appropriate for the most common use cases and for the Android device to derive power from the USB connection. However in order to control a USB Audio interface peripheral, the USB port must operate in “Host” mode. This is the job of the USB “On The Go” (more commonly “OTG” adapter). It both causes the USB port to operate in host mode and provides the USB “A” connector required by those peripherals.
Connecting a Bluetooth MIDI controller.
Though it isn’t obvious that this is true, Android supports Bluetooth MIDI devices, with a caveat. It may seem like the way to pair a Bluetooth MIDI controller would be to put that controller in pairing mode and then go to the Android Bluetooth panel in settings and pair just as one would for Bluetooth headphones or earbuds. Indeed, you will see your MIDI device and can (misleadingly) pair to it, but it will not be functional. To actually connect the controller to the MIDI system it is necessary to use a third-party utility.
“Byte By Byte”?