Woah the random qtes surprised me!
I think you should consider changing the key icons, because it's easy to interpret 'S' as a '5' and 'U' as a 'V' and vice versa.
You're totally right, I just used one of the kenney packs for inputs, and they were good enough for the jam. I do agree some are not that obvious though and given more time I would come up with something better. Thanks for playing!