Yup. For actual singing, altitude can be a killer. Difference between doing a show in San Bernardino (maybe 1000 ft up or so) and not too long after doing a show up in the Sierras (I think we were 6000 ft) is VERY noticeable. Those hold notes just don't hold as long as they would at sea level unless you get acclimation time.

As to the effect on the form of music...

I'd almost say this would be more of an ecological sociology question - different cultures evolve in different conditions. A hunter gatherer society that moves with herd migrations around the plains is NOT going to develop the same society as a primitive hill society dependant on fishing. Song forms are pretty well accepted to be affected by the type of society around them - nonviolent societies aren't going to get much in the way of battle songs, ag communities aren't likely to be as much in for the hunting sagas, etc - and societies are in a way affected by altitude as to how they develop (resources just aren't the same at lower elevations and higher). Singing style is normally a function of culture. So yes, alititude probably affects singing style. I won't say definitely because this is ALL barroom science on my point, and could be complete BS.

M