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Subtractive synthesis is heavily reliant on different wave types to increase the variety of possible sounds. Decades ago, when synth makers were trying to find novel ways to get more milage out of their oscillators they decided upon an interesting solution: Oscillator Sync.

Oscillator sync, sometimes called ‘hard sync’, is achieved when one oscillator, called a master oscillator, is plugged into the sync input of second oscillator, known as the slave oscillator. Each time the master oscillator’s cycle repeats, it resets the cycle of the slave. When the slave’s frequency is set slower than the master’s frequency, the slave is forced to repeat before it finishes a complete cycle. On the other hand, when the slave is tuned faster, it will repeat partway through the second or third cycle such as on the following picture:


In practice, particularly when the slave’s frequency is set higher than the master’s frequency, unique waveforms can be created which are often very rich in harmonics. These extra harmonics can be very useful in subtractive synthesis because it gives a lot content for a filter to carve away.

To use in patch with a keyboard or sequencer:

* Patch from the source’s pitch CV output into both the master and slave oscillator’s pitch CV inputs.

* Patch from one of the master’s output jacks into the hard sync CV input of the slave oscillator.

* Monitor only the slave output.

When you adjust the master’s frequency knob you will hear the pitch raise and lower. When you adjust the slave oscillator’s frequency knob you will hear the timbre of the sound become more complex as you turn the knob clockwise.

An additional fun thing you can do is patch a copy of your amplitude envelope into a CV input on your slave oscillator. If your slave oscillator doesn’t have a dedicated attenuator knob at it’s secondary input then you may want to run your envelope output through an attenuator module first. Now as you open the attenuator, each time a note is triggered by your keyboard or sequencer, a dynamic sync animation will occur.