Google: "speed of sound at sea level vs altitude".
While the speed of sound varies with altitude the reference is to a standard temperature.
Humid air is also less dense therefore lower in pressure and changes
the speed factor accordingly.
For a Pilot operating an Aircraft at 30,000 feet Pressure Altitude becomes a life and death matter but a 5,000 foot difference in a listening room will not change the factor enough to make much difference.
However Caribou Ranch Recordings seem to have some notoriety amongst recording artists.