Here are some instructions for setting up a Raspberry Pi 3B or a Raspberry Pi 4B as a MIDI host for USB or Bluetooth musical equipment. The purpose is to build an as-simple-as-possible device with no user interface that can be switched on and off by simply connecting/disconnecting to/from a power source.
This is being used daily since
months years by hundreds of musicians and by me on the following equipment:
Download the RPi 3 SD image or the RPi 4 SD image (updated with Raspbian Buster released 2020-02-13).
Here's another ready to use image for Raspberry Pi 2B (with optional TP-Link UB400 Bluetooth dongle) kindly provided by Shreyash Agarwal:
Here are the complete instructions
Here's a similar project that uses Pi Zero-W 1.1 enhanced with DIN-MIDI: A minimalistic MIDI interface for the Raspberry Pi