mt32-pi is a free and open-source MIDI synthesizer for the Raspberry Pi series of single-board computers that is inexpensive to build and easy to set up. It is aimed at hobbyists, MIDI enthusiasts, musicians, and retro gamers. The software is a "baremetal" project - no operating system, no Linux - just a small self-contained kernel that starts up in seconds.

The project originally started as an emulation solution for the legendary Roland MT-32 synth module from 1987, using the open-source Munt emulation core. These synthesizers are now hard to find, yet still highly sought-after by fans of vintage PC games which relied heavily on them. With mt32-pi, the popular Raspberry Pi can be transformed into a faithful clone of the MT-32.

mt32-pi recently gained SoundFont support via the FluidSynth engine, which opens up more possibilities, such as General MIDI and Roland GS compatibility. Users can switch between synthesizer engines and SoundFonts at runtime with SysEx commands or a button press.

In its most basic configuration, a Raspberry Pi 3 or above and USB MIDI interface is all that is required. The user can expand it with a Hi-Fi DAC for higher-quality sound, LCD/OLED screens for displaying information, and buttons/knobs for physical control of the device. Users can enjoy fast startup times and and very low latency due to running directly on the hardware.

mt32-pi has inspired hobbyists around the world to build and share their own custom installations and accessories for the project. All-in-one "HAT" boards for the Raspberry Pi (both free and commercial) have been developed that add MIDI input, stereo output, and LCD/OLED displays to the device. The project has also enabled people to try MIDI synthesis for the very first time and discover its flexibility and compatibility with both vintage and modern hardware. mt32-pi is a synthesizer that anyone can build - take a look at the showcase page for ideas and inspiration!

mt32-pi connects to any kind of MIDI-enabled computer, sequencer, or control keyboard by means of the classic DIN connector, which can be added to the Raspberry Pi's GPIO pins with some simple electronics, or an off-the-shelf USB interface. Some classic computers such as the Atari ST, Commodore Amiga, and Sharp X68000 have been popular host devices among vintage games enthusiasts. Music producers have been using mt32-pi as a way of integrating SoundFonts and MT-32 sounds into their live performances.

If you own a MiSTer FPGA computer, you can use mt32-pi to overcome the limitations of the embedded ARM CPU (aka. Hard Processor System, or HPS) and expand its MIDI capabilities. You can then enjoy classic games that make use of the MT-32 for their soundtracks, such as those that can be run on the AO486 core, for example. See the MiSTer FPGA user port connection page for more information.