What the game did was make a MIDI song each time you played a tune, based on your artistry skill. A skilled player would give a fantastic performance, whereas an awful player would play a disastrous tune that is absolutely painful to hear.
Get enough people together and you could do an ensemble performance:
The way it worked was really simple. You just write the music using a short series of letters and numbers, and then the game would poof it into a song that played for everyone.
It was like this:
t#: set the tempo (60-250, or 120 if not set)
v#: set the volume (1-15, or 15 if not set)
l#: set the normal note length (1 for whole notes, 2 for half notes, etc)
a-g: play a note (add a . to do 1.5x length, a + to make it a sharp note, - for a flat note, a number to change that specific note's length)
r: play a rest (add a .to do 1.5 length, and/or a number to change that rest's length)
>: raise octave
The above was taken from: https://mabinogimusic.tumblr.com/post/37689459353/this-is-halloween-the-nightmare-before-christmas
That being said, here's what could be done:
1. Composing / Memorizing songs
You need ways to share songs, and memorize them.
Sharing songs? Maybe they can be written on e-notes. Add a printing type called 'score'?
Memorizing songs? Maybe have slots just like memorize/memory, but for music.
Play a single melody from memory. Add lyrics just like singing normally. Include a URL to the song, have it available for listening for 10 minutes before it goes poof.
There could be a handful of "default" songs for the times you hum aimlessly.
3. Playing an instrument
Play multiple melodies at once on a single instrument.
4. New instruments?
Synthesizers! Turns out there are all sorts of CP sounds in MIDI: https://youtu.be/IYdq06l8qXI
You could have different brands capable of different sounds, and set your channels appropriately:
set channel1 on synthesizer to 84
Grab friends for a jam session and/or sing while playing an instrument.
Prepare a Jam, have people join up like follow / escort, then Jam!
I believe MIDI can support up to 16 channels, one of which is a percussion track.
6. Record and play back songs
Save songs and lyrics on a recording device to be played back on personal players, in vehicles, at clubs, during broadcasts, ambient ads, elevator music, etc.
Have a playlist going in a club nonstop, etc. 😁
That's all I got. I know this would take some time to add. But it would be super cool to hear the world. (Also I hear Cerb has a thing for folks who try to sing. 😉)