My friend who is a much more experienced synthesist than I was telling me how important it was to consider whether the oscillators were synchronized with the gate (and if so, at what phase angle) because it affects the time-domain shape of the attack. He also said that his FFT-based spectrum analyzer showed no change even as the attack shape changed, but that you could still hear the difference.
I was doubtful because my understanding has always been that the ear can’t hear absolute phase and so that’s why, in additive synthesis, even if you randomize the phase of the harmonics, things should still sound the same. It’s particularly striking with squares and ramps; get the phase of even one harmonic wrong, and it looks like something completely different on a scope.
So I wrote a test in Pd, and while I don’t hear any differences in attack, I do hear differences in tone as the phases of the harmonics change. If you’re interested, try my test for yourself. I’m approximating a ramp using 50 harmonics, and you can control the phase of each harmonic using the phaseTable. Trigger the AR envelope with and without sync and see if you can hear a difference. Next, open up the gate so you get a steady tone and play with the phaseTable. You’ll hear the timbre change subtly, especially when changing the lower harmonics. Now I’m not sure I could tell you what phase I’m hearing in a double-blind test, but I do hear a difference. So am I wrong that the ear can’t hear absolute phase? And if I’m not wrong, why do I hear a difference? It sounds different on different speakers/headphones/earbuds so I’m guessing it has to do with asymmetries between the positive and negative excursions of the diaphragm?