Advanced FM: multi-operator voices and instrument emulation

This module moves you from two-operator FM sketches to the whole task of programming a believable acoustic emulation on a six-operator voice — the DX7-lineage skill behind every convincing FM electric piano, brass stab, and bell you hear in a live set. On stage or in a Surge XT/FM8 rig, you rarely have a sampler slot to spare; being able to conjure a brass section or a tuned gamelan bell from six sines, and then bend it expressively, is what makes FM worth its reputation.

The arc starts supported: first internalize that an operator is a bundle (oscillator + scaler + envelope, per “An FM operator bundles an oscillator, a key/velocity scaler, and an envelope”) and why six of them split a voice into three independently-enveloped spectral bands. A first exercise uses algorithm 32’s all-carrier additive mode with staggered harmonic attacks — a safe sandbox where every operator is audible. From there, exercises reintroduce modulation: Chowning’s two-breakpoint index envelope gives you the spectral trajectory of a single note; the brass, woodwind, and percussive parameter recipes then serve as JIT how-to pointers for each acoustic family. Key sync, rate scaling by keyboard position, and the held-steady modulation depth principle keep patches consistent and natural as you play across the range.

The required atoms gate the capstone directly — you cannot justify an algorithm, per-band C:M ratios, index envelopes, and scaling without them, and the perceptual-group-evolution principle is your license to stop chasing exact partial curves. Supporting atoms enrich the result: performance wheel coupling, formant-adjacent tricks from Surge XT routings, EBM bass and drum-texture variants, and post-FM EQ show where the same voice architecture goes next.

Runnable examples

Generated from the context/ instrument corpus by concept (redistributable idioms only). Do not edit — regenerate with gen-module-examples.mjs.

fm-timbre

note("c3").s("sine").fm(4).fmh(2).fmi(3)

_{strudel-0204 · CC0}

osc (midicps 24 * (1 ~~ 4 $ osc 110)) >> audio

_{punctual-0006 · CC0-1.0}

formant-vowel

note("<c3 e3 g3>").vowel("<a e i o>")

_{strudel-0036 · CC0}

d1 $ note "c e g" # sound "supersquare" # vowel "a e i"

_{tidal-0035 · CC0}

additive-synthesis

{ Klang.ar(`[[100, 200, 300, 400], [0.4, 0.3, 0.2, 0.1]]) * 0.1 }.play

_{supercollider-0022 · CC0}