I'm trying to make something that sounds like C64 SID chip. One particular property of that chip is that, it is possible to hard-sync two oscillators, so that the slave oscillators phase is reset to zero every time master oscillators phase returns to zero. I couldn't find a a way to implement this in pd.
Trying to capture the zero crossings on the master oscillator seems to be a dead end, because i'll have to turn it into a control signal somewhere to connect it to the phase input on slave phasor. And control signals are much too slow to catch every zero crossing.