Though it’s still fun to “accidentally” empty it on the snotty flautist sitting in front of you. (I was in 8th grade.)
The bass drum kick pedal on a set works against a spring. Gravity has very little to do with it.
Acoustic or not, most keyboards on the better instruments are weighted to simulate an acoustic model, so they would be adversely affected. Cheaper ones have springs, which would work better in a non-gravity environment.
Pedals of all kinds are spring loaded (keyboard sustain) or have neutral balance (effects), and are not dependent upon gravity.
Harp
Why?
How about grand piano in a marching band?
On a treadmill. That would be awesome.
Most of the weight goes on the end-pin, but there is a bit of weight on the legs. I think the easiest way to play cello in space would be to use Velcro - put a square of it on the ground and on the end-pin, and square of it on the cello and your pants.
Could you put rosin on a bow in space? When you play a string instrument on Earth, the rosin gradually comes off as you play and settles on the wood right below your bow. In space, all that would float into the air, plus the fact that it powders might mean you couldn’t apply it in the first place.
A small grand piano would still have a mass of close to 600 lbs. and a large one about half a ton. When the marching band started – assuming something like velcro boots to keep 'em marching – you’d get left behind, and when they stopped, the guys in front of you would have to learn to duck really fast and would quickly come to hate you and your stupid piano with a passion. Going around corners would be something to behold. 
It doesn’t matter what instrument you play. You couldn’t practice because your metronome wouldn’t work.
Something big like the harp, because when you pull on the string, your pull your body along. With no gravity, there is no friction, and since all the pulling is one way, you’d be gaining momentum … Easily solved with straps or bolts or something…
Piano accordion may be worst in terms of relying on gravity for playing… Sometimes they sit it on the side and let gravity provide compression ?
Tubular Bells? (or anything like a vibraphone/xylophone)
When the glasses are rung by rubbing their rims, it’s called a glass harmonica (mentioned above) - I guess it might be called a glass glockenspiel or glass dulcimer if it is played as a struck instrument.
This instrument would be extremely difficult in zero G.
Yes it would - but both the arm and the body of the metronome would oscillate in opposition (the body not so much, as it’s more massive.
What about bagpipes?
Well, electronic metronomes and such would work, but I don’t think the classic mechanical one would. I’m not a musician so someone can correct me if I’m wrong but my understanding is that the classic mechanical metronome is basically a double-weighted pendulum, where the upper weight adjusts the center of gravity and thus the effective pendulum length and period of oscillation. The only thing the spring does is provide the energy to keep it oscillating. In fact if one considers the metronome a “musical instrument”, the mechanical style would be the classic example of something that would not work in zero gravity.
For most instruments, very little impact other than holding it differently (e.g., guitars, woodwinds). A violinist would have to slightly adjust technique, as would a drummer, due to the lack of gravity when controlling something (bow, drumstick) where gravity has an obvious impact but is far less than the force they normally use.
A piano would not work. A digital piano with weighted keys would not work correctly. (Try this on your DP at home: flip it upside down on the stand, and try to play it. Nope.)
Good point! But no doubt workarounds could be found.
Right.
Good point: the player matters, too!
Good point! A trumpet wouldn’t sound as good in zero-G, unless you had a way to evacuate it periodically. Special zero-G trumpet feature! A spot where you tie a string so you can whirl it around your head, with a spit valve at the opposite end, and of course a collection cup of some sort. oboy.
Drum pedals (bass and hihat) might need to be sprung differently. Digital piano pedals are sprung and don’t need gravity. Digital piano keyboards (“hammer-action keyboards”) don’t work, but organ and synthesizer keyboards do. You can use the latter to play piano, though most piano players detest doing that, for good reason.
Sax, clarinet, and to some extent flute, rest on one or more of your digits. For example, on sax, a tab on the instrument rests against the right thumb, in addition to the neck strap; the other fingers are free to press keys. Without the weight of the sax, it would float up. Perhaps the tab could be replaced with a loop without losing too much flexibility for the player. (The mouth also helps hold the instrument, of course.)
Good point, but probably manageable.
While hammer-action keyboard assemblies are more expensive than synthesizer or organ-style keyboard assemblies, there are expensive pro-quality instruments with the latter. It’s a matter of instrument style. But you’re right that hammer-action keyboards require gravity.
lol. My metronome works, because it’s on my smartphone. It just looks like a mechanical metronome.
I only played bagpipes once. Zero G would have overcome my main concern, which was passing out. I might still pass out, but wouldn’t fall and knock my head! But wow, what a full-body, physical instrument! Right up there with accordion. I bet you think I’m joking, but I’m not.
Both drums and flutes are played continously to placate the daemon sultan Azathoth ruling all time and space from a curiously environed black throne at the centre of Chaos.
And… is weightlessness involved?