I spent this evening making some audio recordings with my breadboard to show the new software options (Quirk Modes). I've got a tune from FF7 and a tune from Descent this time. This song from FF7 is "Can you Hear the Cry of the Planet?" which is the song that plays in the Forgotten Capital.
First we have "Normal/Stereo"
FF7_Can_You_Hear_NORMAL.mp3
Next is the single synth voice -- everything but percussion is set to patch 81 -- Synth Saw Wave. This is the default for this quirk mode but you can set it to any patch you like via a midi command.
FF7_Can_You_Hear_SINGLEVOICE.mp3
Next up we have the "Boken MIDI" quirk mode. This one started by preventing the computer from setting the patches when a file loads -- but I realized you could do the same thing with the single synth voice mode by setting it to 00 -- piano. Now it re-assigns all the patches to be one of four options I've selected instead. Seems to sound good with a variety of tracks, but can be odd depending on the original patches. I could make this configurable but you'd have to send four different midi commands to do it, and it wouldn't persist through powercycles. Seems to be a lot of effort for a limited gain.
FF7_Can_You_Hear_BROKEN.mp3
Next is the low polyphony option -- configurable to limit the synth to between 1 and 15 voices with a midi command. It's set to 5 in this example. Kind of like what the NES did when it needed to stop playing a note to play a sound effect, but more random.
FF7_Can_You_Hear_LOWPOLY.mp3
Finally, we have the MIDI RANDOMIZER. Every time the computer sets a midi program/patch, the synth will randomly assign one based on one of 128 user selectable seeds. If you reset the reset to the same seed between plays you should (usually) get the same combinations. Left and Right ATMega328s will choose different voices. Can be subjectively bad, but sometimes has a cool stereo effect. This is seed 18:
FF7_Can_You_Hear_RANDOMIZER.mp3