PJRC forum member honey_the_codewitch has created the Prang Pro, a Teensy 4.1-based “MIDI score sampler.” Prang intercepts MIDI messages and triggers entire MIDI files when a key is pressed, creating sort of “I heard you like MIDI, so we put MIDI in your MIDI” backing track launching system, over which you may play unmapped notes.

The project began as an FL Studio plugin, but after encountering limitations, the switch was made to hardware, initially using an ESP32-S3-based board (pictured above). Switching to Teensy 4.1 meant easier USB MIDI, built-in mSD, and better performance. The PlatformIO project is available on GitHub, and you can see it in action in the video below.