"Soft Sync is a tool that enables you to create a soft sync effect, which reverses the phase of the oscillator according to the master oscillator's polarity by using FM. To operate, connect the output of the master oscillator to the sync input and connect a frequency input (from MVC, Pitch2CV etc) to Freq.
Then connect the frequency output to the carrier oscillator's Freq input." (Flexor Manual)
dspLoad 2,50/5.60/2.50 Poly16