Fitting the MT32 Pi Zero HAT and configuring the software

This post will provide the information you need for setting up my Pi Zero HAT for MT32-Pi.

Note that to run MT32-Pi, a Pi Zero 2W is required. The HAT will work with a regular Pi (3 or above) but obviously the form factor is designed to go with the Zero. 

Four long screws and nuts are provided, with standoffs and washers. The standoff isn't quite long enough and so the washer goes alongside it between the boards to give the extra mm of hight. 

Don't push the HAT all the way home, that'll help with the fiddly job of fitting the washer and standoff. 

With the nuts fitted finger-tight, you may like to trim off the extra length.


If I didn't supply an SD card containing the software, then you can find that here:

See Dale's instructions for creating your SD card here:

You'll need to do some configuration of the file mt32-pi.cfg This is very easy, just open it in any notepad-style text editor.

Make sure that MIDI over USB is enabled - this should read usb = on


Enable audio via the DAC on the HAT by changing this line to read output_device = i2s


Enable the 4-button system by changing this line to read scheme = simple_buttons

This one is optional. A real MT32 responds to channels 2-9 and 10. You can alter this to an alternative channel mapping if the instrument or controller you want to use sends on channel 1. This setting makes the MT32 respond to channels 1-8 and 10.


Enable the screen on the HAT by setting this line to read type = ssd1306_i2c


The options just below that should already be correct; width = 128, height = 32, i2c_lcd_address = 3c, rotation and mirror = normal

I think everything else should be correct or not applicable. You may like to read the file and see whether there's anything else you'd like to change. But only do this after making the above changes and confirming that your HAT / MT32-Pi installation works. 

Control scheme

The 4-button control scheme works as follows:

Button 1 Switch synthesizer

Button 2 Switch MT-32 ROM or SoundFont

Button 3 Decrease volume

Button 4 Increase volume

Button 1 will switch between MT32 mode, which will use the MT32 ROM(s) that you have in your roms directory, and General MIDI mode, which uses any soundfonts that you have installed in the soundfonts directory on your card. 

When in General MIDI mode (aka soundfont mode), the second button will switch between any soundfonts that you have in your sountfonts directory. See the config file for specifying the default.

Buttons 3 & 4 are self-explanatory. Unfortunately they step the volume from 100-0 one step at a time, and there's no 'hold to go fast' option. 

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