The source is still vibrating at whatever frequency it's vibrating at.
ok - got it, no change at source..
but if it can propagate through the medium (air), faster in condition A rather than condition B would that result in a relative change of pitch to an observer particular point of distance?
or is it as case of reduced signal decay in hotter conditions rather than colder conditions?
(not a physicist - a lapsed research scientist of a different color)