@kymarto are you sure about this? I cannot readily find back the source, but I had in mind that for example a trombone can produce up to 3W of sound power (and a symphonic orchestra at ff dynamic, around 100W). Obviously a trombone player doesn't input 300W. Something doesn't look right....... In fact, even in the most efficient instrument, 99% of the energy input is lost to the walls (and mechanical losses at the reed), only 1% emerges as sound.
EDIT: it was my memory that's off by a factor of 100. Sorry!