My guitars seem to sound different at high altitude. Santa Fe is 7000 feet above sea level and the air is thinner here. Is this because the sound from the guitar has to push less air at this altitude?

I also noticed an incredible difference in the sound depending on the humidity in the air. Usually Santa Fe has very low humidity, around 40%. But every once in a while after a summer rainstorm the humidity rises to about 70%. I noticed that the guitar seems to sound much clearer and purer the lower the humidity.

Lack of humidity can destroy a wooden instrument, but I never humidify my guitars and they have been fine for many years.