What are the limitations of performing music in space? Canadian astronaut Chris Hadfield's song Space Oddity is making news around the world today. It makes me wonder: What are the limitations of performing music in space? Clearly, there is no point to play music when there is no air. To make the question more meaningful, let's assume that we are inside a space craft where there is air. In such case: Are there any musical instruments that would be affected by the lack of gravity (and in what ways)? For example, Chris can be seen playing guitar and I assume it works just fine up there. The only example of a musical instrument that I could come up with which would not work, is a glass harp. Any other ideas?
 A: Some instruments would require modifications in order to facilitate playing them. Large instruments would need to be strapped down, and something like a double bass or drums would probably require its player to be strapped into a harness in order to prevent them from pushing themselves off as they played and floating away from the instrument. I can imagine that it would take some time to develop a technique for playing the drums without the assistance of gravity, though I suspect it would be possible.
Other instruments would require modification in order to be played at all. Pianos, for example, rely on gravity to return the keys and hammers to their original position after releasing a key, so a piano wouldn't work without modification. (You would probably have to introduce springs to replace the action of gravity, and it would probably be hard to replicate the traditional feel of the keys' movement.)
It's also possible that a grand piano would need to be re-tuned, because its bass strings are long and heavy enough that the lack of gravity might make a (barely) audible difference to their frequency. (But I would expect a piano to need tuning after being launched into space anyway.)
It's surprisingly hard to think of instruments that fundamentally rely on gravity, and which therefore wouldn't work at all. There are a few though - they include the glass harp and rainstick that you mentioned, as well as the waterphone. Speaking of water-based instruments, a hydraulophone would probably work but would make a terrible mess.
However, most small, hand-held string, brass and woodwind instruments would work just the same as on Earth, just like the guitar does. 
The air pressure on a spacecraft might be different from on Earth's atmospheric pressure. You might expect brass and woodwind instruments to have tuning issues in such a situation, but in fact they wouldn't. This is because the frequency is determined by the speed of sound. The air is a good approximation to an ideal gas, and (perhaps surprisingly) for ideal gases the speed of sound doesn't depend on pressure but only on temperature. However, if the air's composition is different (e.g. pure oxygen instead of an $\mathrm{O_2}$-$\mathrm{N_2}$ mixture) then the change in density might cause tuning issues for these instruments, for the same reason that helium makes your voice go squeaky. This issue will not affect the tuning of stringed instruments, though it might affect their tone slightly by changing the resonant frequencies of their body. 
Of course, the really interesting question is whether there are any instruments that could only be played in microgravity. I can't think of any ideas off the top of my head, but it's an interesting thing to think about.
A: There are several things that have to be considered in space, microgravity or not.

*

*"There is no evidence that human auditory functioning changes in space." Source: MSIS


*Microgravity means no natural air circulation. Hence, fans have to keep working, and they are ridiculously noisy. It is not practical to have long concerts in space due to carbon dioxide and heat buildup in the bubble around the performer.


*Some manned spacecraft are designed for lower air pressure and/or different gas composition, which changes the frequency content of speech, song and musical instruments.


*Internal spaces in manned spacecraft are not optimized for music. When communication by speech is required, reverberation time is set at 0.5 seconds. Source: MSIS 5.4.3.2.2.1
Although only #2 above is directly related to micro-g environments, thought you had to know other constraints as well.
EDIT: for a slightly more involved performance in space, watch this clip (Ian Anderson and Catherine "Cady" Coleman).
EDIT #2:
Source: http://spaceflight.nasa.gov/feedback/expert/answer/isscrew/expedition7/index4.html

From: Alain Haezebaert, Mennecy, Essonne, France, Age: 56
Question: On one of the last ISS pictures I saw was a music keyboard with Ed and Yuri dressed in Hawaiian native shirts. I don't know who is playing piano but my question is: Due to the lack of gravity is it more difficult or easier to play and finally are the sounds the same as on Earth.
Lu: Most definitely, yes. Because, first off, just pressing on the pedals - pressing on the keyboard - will push you away from the keyboard. You need something to strap yourself down. What I first set up was a couple of, basically, straps that you could put your feet in and hold yourself there. But I found out that didn't work very well, because you also have to put a pedal down there. When you press on the pedal on one side, it pushes your body. So it has a tendency to flip you upside down. You couldn't play for very long because you would slowly twist out of position. So beyond that I have to rig up sort of a seatbelt type arrangement that actually holds me into the little table that the piano is mounted on. Even that still doesn't work quite as well, but I'm still working on it.

