I live at 6300 feet altitude in Lake Tahoe, Nevada.  My little Seeburg
"L" loves it up here as much as at sea level.

The bigger problem with subjecting these instruments to high altitude
is the associated lack of humidity.  As the wooden parts dry out and
shrink, more vacuum is required to feed the leaks that get ever worse
over time.  Mr. Rhodes hit the nail squarely on the head with his
explanation of pressure differential.

Roy Clason