Operator
Deep-dive into Live's 4-operator FM/additive synth — algorithms, waveforms, Fixed mode, loopable envelopes, filter, LFO, pitch envelope and the ratio tables behind bells, metal and bass — with eight signature patches.
Operator is a four-oscillator FM synth where every oscillator can also be an additive waveform, every envelope can loop at beat rates, and the whole thing costs almost nothing in CPU. That makes it the right tool for sub bass, FM bass, bells, metallic percussion and the kind of digital leads that need to cut rather than smear. This page assumes you have read the synthesis primer, particularly the FM section.
Architecture
Four oscillators (A, B, C, D) are wired by the Algorithm. Oscillators on the bottom row of the algorithm icon are carriers (you hear them); the ones above are modulators (they bend the phase of what is below). The sum of the carriers goes through one filter, one amplifier with a global volume envelope, and the Spread stereo stage. Three global modulators (LFO, Pitch envelope, Filter envelope) plus each oscillator's own envelope move everything.
The eleven algorithms
The selector shows them left to right, roughly from "most FM" (one carrier, three stacked modulators) to "pure additive" (four carriers in parallel). Letters below read modulator → carrier; the icon in the device is the ground truth, so match the diagram shape rather than the number if your build orders them differently.
Parameters that matter
| Section | Parameter | What it does | Starting points |
|---|---|---|---|
| Oscillator | Wave | Sine, Saw, Square and Triangle families at different band-limits (the number is how many partials), Noise Looped / Noise White, and User (draw up to 64 partials in the display, Repeat tiles the drawing) | Sine for carriers and modulators; use band-limited Saw/Square only on carriers |
| Oscillator | Coarse / Fine | Frequency multiple of the played note (ratio) and fine fraction | Coarse 1–4 integer for harmonic; Fine for detune and inharmonic |
| Oscillator | Fixed | Oscillator ignores key, runs at Freq × Multi in Hz | Modulators fixed at 50–400 Hz for growls; carriers fixed for drums |
| Oscillator | Level | Carrier: loudness. Modulator: FM index (brightness) | Modulators −24 to −6 dB; 0 dB is extreme |
| Oscillator | Feedback | Oscillator modulates its own phase: sine turns toward saw | 10–40% for bass grit, 100% for noise |
| Envelopes | A/D/S/R + Init/Peak/End levels + Loop | Each oscillator, filter and pitch has its own; Loop modes None, Trigger, Loop, Beat, Sync | See loop table below |
| Filter | Type, Circuit, Freq, Res, Drive, Env, Key | LP/HP/BP/Notch/Morph with Clean/OSR/MS2/SMP/PRD circuits | MS2 LP with Drive 20% for warmth; OSR for aggressive resonance |
| LFO | Wave, Rate (free or synced), Amount, destinations | Sine, Tri, Saw up/down, Square, S&H, Noise; modulates per-osc levels, filter, pitch | S&H to osc B level for random FM bite |
| Pitch env | Amount, destinations per osc | Envelope on pitch, selectable per oscillator | +24 st, decay 40 ms for kicks |
| Global | Spread | Detuned stereo copy of the voice | 0 on bass, 30–60% on leads and pads |
| Global | Tone | Attenuates high partials of waveforms, controls aliasing character | 50–70% normally; 100% for deliberate hash |
| Global | Time | Scales all envelope times at once | Macro it: one knob for pluck → pad |
| Global | Voices, Glide, Transpose, Hi-Q | Polyphony, portamento (mono), global tune, oscillator interpolation | Voices 1 + Glide 60 ms for bass; Hi-Q on |
Envelope loop modes
| Mode | Behaviour | Use |
|---|---|---|
| None | Standard ADSR | Everything normal |
| Trigger | Runs attack-decay to End level once, ignores note-off for sustain | Fixed-length hits: drums, plucks that always decay the same |
| Loop | Repeats attack and decay while held, free-running time | Trills, tremolo on a modulator = rhythmic FM |
| Beat | Loops attack-decay retriggered at a note value (Repeat) | Tempo-locked wobble on the modulator level, gated pads |
| Sync | Like Beat but phase-locked to the song grid | Rhythmic patterns that stay aligned to the bar when notes start late |
Ratio table
| Sound | Carrier : modulator | Index (mod level) | Notes |
|---|---|---|---|
| Sub / clean bass | 1 : 1 | −30 to −12 dB | Saw-like sidebands; index controls brightness |
| Hollow / square bass | 1 : 2 | −18 to −10 dB | Odd harmonics only |
| Tubular bell | 1 : 3.5 | −14 dB, long decay | Classic DX bell; modulator decays faster than carrier |
| Metallic hit | Fixed modulator 1.3–3 kHz | −8 dB, 30 ms decay | Per-note inharmonic, cymbal-ish |
| Growl / vowel | Carrier 1, modulator Fixed 60–200 Hz | −12 dB | Timbre changes across the keyboard; automate Freq |
| Kick | 1 : 1, pitch env +36 st, 30 ms | −20 dB | Index gives the click |
Techniques
1:1 FM bass with velocity index
The patch that defines Operator. One sine modulating another at the same frequency: brightness follows how hard you play.
- Algorithm 1. Osc A Sine, Coarse 1, Level 0 dB. Osc B Sine, Coarse 1, Level −14 dB. C and D off.
- Osc B Vel 60%: velocity now scales FM index, so accents are brighter, not just louder.
- Osc B envelope: Attack 0, Decay 350 ms, Sustain −12 dB, Release 100 ms. The attack of each note is brighter than its body.
- Voices 1, Glide on at 40 ms, R< on both oscillators so every note starts identical.
- Feedback on Osc B 15% for a saw-ish edge without a second ratio.
| Parameter | Value | Why |
|---|---|---|
| Osc B level | −20 → −8 dB | The whole timbre lives here; map it to a macro |
| Osc B decay | 200–500 ms | Brightness envelope; shorter = pluckier |
Sub plus FM layer in one patch (Algorithm 5)
Algorithm 5 leaves A as a clean carrier while D→C→B makes the growl. One instrument, two layers, phase-locked by design.
- Algorithm 5. Osc A Sine Coarse 1, Level −3 dB: the sub. Give A its own envelope with Sustain 0 dB.
- Osc B Sine Coarse 2, Level −8 dB: the audible layer one octave up. Osc C Fixed on, Freq 90 Hz, Level −12 dB. Osc D Coarse 1, Level −18 dB.
- Filter on: HP at 60 Hz applies to the sum, so set it below the sub. Instead, use Roar's Multiband routing after the synth and drive only the mid band.
- LFO synced 1/4, Sine, to Osc C level 40%: the growl wobbles while the sub does not.
Tubular bell (1 : 3.5)
The DX7 bell idea. Carrier at 1, modulator at 3.5: the sidebands sit at non-integer multiples, which the ear reads as metal.
- Algorithm 7 (two pairs). Pair one: C Sine Coarse 1, D Sine Coarse 3, Fine 500 (3.5), D level −14 dB.
- Pair two: A Sine Coarse 2, B Coarse 7, Fine 100 (7.1), B level −20 dB, A level −10 dB. This adds the high shimmer.
- Envelopes: all four Attack 0. Carriers Decay 4 s, Sustain −inf, Release 3 s. Modulators Decay 1.2 s: the bell gets purer as it rings.
- Pitch envelope: +0.3 st, Decay 15 ms on D only, for a strike transient.
- Spread 40%, Tone 60%.
Synth kick with pitch envelope and Trigger mode
A sine with a fast pitch drop, a click from a short burst of FM, and envelopes in Trigger mode so every hit is identical regardless of note length.
- Osc A Sine, Fixed on, Freq 48, Multi 1. Level 0 dB. Envelope: A 0, D 450 ms, S −inf, Loop Trigger.
- Pitch envelope: amount 100%, Peak +36 st, Decay 35 ms, End 0, destination A only.
- Osc B Sine, Coarse 1 (relative to A's fixed pitch), Level −10 dB, envelope D 20 ms, Loop Trigger. This is the click.
- R< on both oscillators. Voices 1. Filter off.
| Parameter | Value | Why |
|---|---|---|
| Pitch env decay | 20–60 ms | Shorter = tighter techno; longer = 808 boom |
| Osc A decay | 200–900 ms | Body length; match to tempo gap |
| Fixed freq | 40–60 Hz | Tune to the key of the track, then forget it |
Beat-mode envelope wobble without an LFO
Set a modulator's envelope to Beat with Repeat at 1/8: the index re-attacks every eighth note, tempo-locked, with a shape you draw rather than a sine you get.
- Build the 1:1 FM bass. On Osc B envelope: Loop mode Beat, Repeat 1/8, Attack 30 ms, Decay 180 ms, Sustain −inf.
- Change Repeat to 1/16 for a double-time wobble; set it to a triplet value for swing.
- Switch to Sync mode when playing live so the wobble stays on the grid even if your note starts late.
Additive organ and drawn harmonics (Algorithm 11)
Four carriers in parallel, each with a user-drawn partial set, is a 256-partial additive synth. For an organ, each oscillator is a drawbar group.
- Algorithm 11. Osc A: Wave User, draw partials 1 and 2 at full. Osc B: partial 3 at 70%. Osc C: partials 4 and 8 at 50%. Osc D: Sine at Coarse 16, −20 dB for the top drawbar.
- All envelopes: Attack 5 ms, Sustain 0 dB, Release 40 ms. Organs have no decay.
- LFO Sine 6 Hz to all oscillator levels at 10%: tremolo. Map Rate to a macro for the slow/fast switch.
Fixed-frequency metallic percussion
Set the modulator to a Fixed frequency in the kHz range and the carrier to a fixed note: the result is a cymbal-ish inharmonic cluster that does not change with key, perfect for Drum Rack pads.
- Algorithm 4 (three modulators into A). A Sine Fixed 220 Hz, envelope D 300 ms Trigger.
- B, C, D all Fixed: 1700, 2900, 4300 Hz, levels −6, −9, −12 dB. Envelopes D 60–150 ms.
- Add Noise White on D instead of a sine for a hi-hat-style spray; keep Feedback at 30%.
- Velocity to all modulator levels for dynamic brightness. Tone 100% for deliberate aliasing hash.
Feedback saw lead with Spread and Glide
Turn a sine into a saw using Feedback instead of a Saw waveform: the harmonics are generated per note and respond to level, and the oscillator stays alias-free at high Tone.
- Algorithm 7. Osc A Sine, Feedback 45%. Osc C Sine, Feedback 45%, Fine +8 cents. B and D at −30 dB, ratio 1, as subtle index.
- Voices 1 (mono), Glide 90 ms, Retrigger off. Spread 55% for stereo copies.
- Filter MS2 Low-pass 2.5 kHz, Res 15%, Drive 30%. Filter envelope +18 st, Decay 300 ms.
Presets to build first
- Sine sub (A only, Voices 1, Glide 30 ms). Save as the default.
- 1:1 FM bass with velocity index and the Beat-mode wobble as a Macro Variation.
- Algorithm 5 sub-plus-growl, with Osc C Freq and Osc D level on macros.
- Trigger-mode kick, pitch env decay on a macro, in a Drum Rack pad.
- 3.5 bell with Spread, to a Hybrid Reverb return.
- Fixed-frequency metal set: three pads with different fixed trios.
- Feedback lead with Glide and delayed vibrato.
- Algorithm 11 organ with tremolo rate macro.