Fantastic to have you back,
@Prok . Was about to go to sleep but had to write up a comment when I saw this pop up.
As for the instrument selection...
[] The Cello (watch out for your foot, and your scrotum)
If someone's trained in it, or isn't comfortable messing around with the sounds of household items, leave it to 'em. Neither of those apply to Jaune, so I don't really see a need to go for it.
[] The Marbles. (Low and warm, glass and metal rolling across wood, scrrrrrrrrrrrrrrr-)
Very versatile - you can get a humming sound from rolling, a sharp clack or chime against other marbles or a solid surface, a rattle or rainfall patter if you put them in a bag...
It's great on a technical level, but I'm not sure it "fits" Jaune in particular?
[] The Rosary. (Tiny little tandem staccato beats, tiktiktiktiktiktik-)
A lot less versatile than the marbles. Being made of wood does give them a warmer timbre, but its a lot harder to get much variation out of them - not even just outright different use cases, but even notes within the main use case.
[] The Jacks. (Little metal snowflakes, tinkling away against the table and each other.)
Similar to the marbles, but I suspect they'll be a fair bit quieter.
[] The Little Metal Cup. (You should probably leave this to Weiss, she has better nails to tinktatinktatink against this thing.)
Cups are great instruments. Rapping against the side, as Jaune suggested, sure, but there's also tapping the whole cup against something, rolling it around, blowing over the lip, filling it up with stuff to change the sound it makes, stretching something over it and using it as a drum...
[] Moleskin Diary and Cards. (Deep layered thumps and scritches, the sound of 52 cards and 150 pages moving in tandem.)
A fair amount of versatility here, if not as much as the marbles or cup, but I kinda like how it ties into Jaune as a person. Write out some math in the notebook, Jaune!
[] Little Brass Gear Cube. (You genuinely have no idea what this is, but you know what sound gears make.)
Tempting to wildly speculate that it's some secret Ozpin contraption or something, but I'm betting it's just a fidget spinner. Could maybe get some neat sounds out of it if it's hollow inside, but a solid metal cube is hard to get a lot of music out of, and gear meshing noises are alright but limited.
[] Root Vegetables. (Snap! Crunch!! But you can only use each one once. Who ever heard of an instrument you can only use once?)
Kinda ties into the idea of audio sampling there - in a real production Jaune could easily just use the Transistor to sample audio from the outside and then loop and distort it. I'm guessing that would be firmly against the spirit of the exercise, though - something along the lines of "music is all around us, it isn't something that's rigid and only found in one place or that relies on specific tools or methods".
[] … Sunglasses? (You'd be better off just wearing them, honestly.)
Can't get much sound out of sunglasses period unless you smash them, but there's a ton of music you can make with just the human body. Singing, obviously (and what I expect Weiss to settle on in this exercise, honestly, since she's got proper training in it and it fits the lesson), but also clapping, humming, slapping your knees...
[] The Bass (Any idiot can play the bass, but it takes a special kind of idiot to play it well.)
Another proper instrument.
My general thoughts are something like: There's no need to reinvent the wheel if you don't
have to, and the bass and cello
are ultimately literally designed to make pleasing sounds when played. If someone has experience with brass or strings, they should grab those.
Weiss can just sing, fivehead. Or she might be the one on bass or cello, I could see her musical training extending to that.
For the people who don't have existing experience with brass or strings, they aren't likely to get much better sound out of the bass and cello than they would out of the marbles or cup, so they should go for those and try to stir up their creativity, at least.