Hard sync: definition
With oscillator sync (hard sync), a “slave” oscillator is reset to the start of its cycle every time the “master” oscillator begins its own. The perceived pitch stays that of the master; changing the slave's frequency instead changes the harmonic content, with formant-like peaks. Moving the slave with an envelope or an LFO gives the typical “tearing” sound of sync leads.
How it sounds and why
If the slave is at a higher frequency than the master, each master cycle contains “pieces” of slave cycles cut off abruptly: the discontinuity generates many harmonics and a zone of energy around the slave's frequency. As the slave rises, the zone rises: it sounds like a resonant band-pass filter opening, but with a more metallic and aggressive character.
- Soft sync: the reset happens only under certain conditions or reverses the direction of the wave; the result is softer (some analog synths and Vital/Serum offer it).
- In Serum and Vital it exists as “warp sync”: it simulates sync inside a single oscillator.
Typical uses
- Rock/new wave leads: The Cars, “Let's Go” (1979), is often cited as a classic example of a sync lead (Prophet-5).
- EDM and synthwave leads that “scream” in the chorus.
- Sync basses for electro and techno: fast envelope on the slave's frequency.
- Zaps and lasers: fast slave sweep.
Basic recipe
Osc 1 (master) saw or square at zero (or low) volume, osc 2 (slave) synced saw; dedicated envelope on osc 2's pitch: amount +24/+36 semitones, attack 0, decay 300–600 ms, sustain 20–30%. Slow LFO (0.2 Hz) for movement during long notes. Open LP filter (5–8 kHz) to contain the harshness, then delay and reverb.
Ring modulation: definition
Ring modulation (RM) multiplies two signals. The result contains the sum and difference frequencies and (in pure RM) does not contain the original frequencies. With two sine waves at 440 and 300 Hz: output at 740 Hz and 140 Hz. With rich sounds the combinations multiply and the spectrum becomes inharmonic: bells, metals, robotic voices. Amplitude modulation (AM) is similar but keeps the carrier.
Uses of RM
- Bells and metallic percussion (two square waves at a non-integer ratio: the 808 cowbell and cymbals use related principles of combined oscillators).
- Robotic voices: the Dalek voices in the series Doctor Who were created at the BBC with a low-frequency ring modulator (about 30 Hz) on the voice.
- Dirtying up a bass or a lead with a modulator that follows the note (tracking) to keep the pitch: with integer ratios (1:1, 1:2) the result stays harmonic.
- Fast tremolo and “growl” with modulators at 20–80 Hz.
Tools
Sync and RM are found on almost all analog and virtual synths: Prophet-5 V, Jup-8 V, ARP 2600 V (dedicated ring mod), Korg MS-20 V (ring mod), CZ V (ring between the lines), Mini V (the original has no native sync; the Arturia version adds functions). In FL Studio: 3x Osc can use the third oscillator as an amplitude modulator for the other two (AM option: with an audio-rate oscillator the result is close to ring modulation), Sytrus (RM matrix between the operators). For ring modulation on audio tracks you need dedicated effects: Kilohearts Ring Mod (in the free Essentials pack), Ableton Frequency Shifter in Ring mode, or a frequency shifter such as the free Valhalla FreqEcho for related effects.
Example in A minor
Chorus lead at 128 BPM over Am – F – C – G: melody E5 – D5 – C5 – A4 with a sync lead (slave envelope +30 semitones, decay 400 ms), glide 40 ms, 3-voice unison. RM bell with two sine waves (ratio 1:1.47) doubling the long notes an octave above, decay 1.5 s.
Common mistakes
- Sync without slave movement: static, anonymous sound.
- RM with random ratios on melodic parts: they detune the harmony.
- Levels: both techniques create a lot of high end, so control 3–6 kHz with a dynamic EQ.
Exercise
- In a synth with sync, record a 4-bar sweep of the slave frequency and compare it with a resonant filter sweep.
- With RM between two sine waves, create three sounds: bell (non-integer ratio), “octave up” (1:1 ratio with offset), tremolo (modulator at 8 Hz).
Related topics
“Subtractive synthesis”, “FM synthesis”, “Filters”, “Lead design”, “Drum design: snare and hi-hat”.