First off close the voltage source switch to start the oscillators. Than close the central switch to synchronize the two oscillators.
Replace MOSFETs with TRIACs
5v = C6 = 1047 Hz
2.5v = C5 = 523 Hz
1.25v = C4 = 262 Hz
0.625v = C3 = 131 Hz
0.3125v = C2 = 65 Hz
0.15625 = C1 = 33 Hz
