I've had this problem before, can't recall if I solved it. This Mac happens to be playing flat, about a half-step. I tested a 440 Hz tone from a keyboard (I checked its mastertune and scale), and to get Pd to play that pitch takes about 451.2 (less than a half step, but way off).
I checked the sampling rates, everything is set to 44.1 kHz. And the ratio doesn't correspond to 48000/44100. I know it's not just the keyboard, because I noticed it in a composition first.. How could something like this happen?
-Chuckk
-- "It is not when truth is dirty, but when it is shallow, that the lover of knowledge is reluctant to step into its waters." -Friedrich Nietzsche, "Thus Spoke Zarathustra"