Can't tell you how many times I've had to transpose or drop tuning because a singer couldn't hit the high notes. No way to get around transposing when you're playing a sax, *used* be no way to get around it when you were playing piano or a Hammond. These days, however, some keyboards can simply be tuned down electronically (ask Eddie Van Halen about that). Guitar can be handled electronically as well -- Variax guitars can be run up or down up to an octave in either direction without changing string tension. That's nice if you've learned the solos in one tuning (and have some open-string chording going on. All you have to do is turn a knob and you're two steps down. So you just play it the way you learned it.