Sorry in advance, I know nothing about music software at all.
Once I was at a friend's house and we were messing around with some piano music software that they could change the sounds of. Like you could change it so each note was a weird squishy alien noise, or a bird chirp noise or a bunch of other things. What software could this have been? it was a long time ago so I don't remember but I want to be able to use it now