There is a growing collection of useful C and C++ MIDI libraries and demo projects available on GitHub. Highlights include a USB MIDI Host Driver and Bluetooth MIDI driver. Demo projects include a Bluetooth MIDI to USB MIDI host converter, a USB MIDI Host to 5-pin DIN MIDI Converter, a 2 IN 6 OUT USB MIDI interface, and a USB MIDI Host to USB MIDI Device filter/processor. Almost all software is MIT license.

For more details, see https://rppicomidi.github.io/ or https://github.com/rppicomidi