strudel-sound-design

name: strudel-sound-design description: The craft of synthesis for electronic music — subtractive signal flow (osc → filter → amp), waveform character and when to use each, ADSR + filter envelopes for movement, FM synthesis and harmonicity ratios, detune/unison for width, sub/body/air layering, saturation and "expensive" sound. Use when a synth sounds thin, cheap, or static; when you need to design a pad / bass / lead / pluck; when FM tones are wanted; when someone says "fatten it", "add movement", "make it breathe", or "the filter sounds dead". Complements [[strudel-effects]] (filter/reverb mechanics) and [[strudel-pro-tips]] (the shortlist of high-leverage moves).

Movement is the difference between a sound and a voice. A static waveform through a static filter is a tone generator; everything below is about making it respond, breathe, and develop.

The subtractive signal chain

oscillator (harmonics) → filter (sculpt) → amp (shape volume) → effects

Every parameter in that chain can be modulated over time — that's the whole game. Static = cheap. Moving = alive.

Oscillator waveforms — what they're FOR

Non-obvious: a single saw is thin. Two slightly detuned saws are a pad. Ten are a supersaw. The waveform choice is just the starting material; the count and spacing of oscillators shapes the character.

ADSR — amplitude envelope

• Attack: how long until peak. Fast attack = percussive/pluck. Slow attack (>300ms) = pad swell, listener's ear "fills in" before the sound arrives.
• Decay: how long to fall to sustain. Short decay on a high-sustain sound = punch with body. Long decay + low sustain = pluck that fades.
• Sustain: the held level. Not a time — it's the floor. Pads: high. Plucks: zero (or near). Organ: full (no decay shape needed).
• Release: after note-off. Staccato = near zero. Legato pad = 0.5–3s. Let the tail breathe.

In Strudel: .attack(.01).decay(.2).sustain(.5).release(.8) — all in seconds/level.

Common mistake: default values everywhere. Every sound needs deliberate ADSR or it sounds like a preset you didn't open.

Filter envelopes — where "expensive" starts

A static lpf is a tone control. A moving lpf is an instrument.

// Static — flat, cheap
note("C3").s("sawtooth").lpf(800)

// Filter envelope — the cutoff moves per-note: bright attack, dark sustain
note("C3").s("sawtooth").lpf(400).lpa(.05).lpd(.3).lps(0).lpe(5)

• .lpf(N) — base cutoff (the "floor" the envelope returns to)
• .lpa(t) — attack time (how fast the filter opens)
• .lpd(t) — decay time (how fast it closes back)
• .lps(n) — sustain level (0 = fully closed at sustain; 1 = stays open)
• .lpe(N) — envelope depth (multiplier; 2–8 is typical; negative inverts)
• .lpq(N) — resonance/Q (0–50; adds a peak at the cutoff; use 2–8 for warmth, 15–30 for acid screech)

The rule: decay + low sustain → pluck. Slow attack + high sustain → swell. Depth (.lpe) controls how dramatic. Start at .lpe(4) and adjust.

Filter resonance as timbre: moderate Q (4–10) adds warmth and body. High Q (20+) becomes a siren. Low Q (0–2) is transparent. Q is not just for emphasis — it shapes the whole tonal character.

FM synthesis — harmonic vs. inharmonic

FM = modulator oscillator changes the frequency of a carrier oscillator, creating sidebands. The harmonicity ratio between modulator and carrier determines whether those sidebands are musical:

• Integer ratios (1:1, 2:1, 3:1) → harmonic series → organ, piano, bells
• Simple fractions (1.5:1, 2.5:1) → slightly clangy but tonal
• Inharmonic ratios (2:1.29, 6:1.41) → metallic, bell-like, gong, noise

In Strudel:

// Warm FM organ (harmonic)
note("C3").s("sine").fm(3).fmh(2)

// Metallic/bell (inharmonic ratio)
note("C4").s("sine").fm(5).fmh(1.41).attack(.01).decay(.4).sustain(0)

// FM pluck: high initial FM depth, decays away
note("C3").s("sine").fm(6).fmatt(.01).fmdec(.2).fmsus(0)

• .fm(N) — modulation depth (0 = pure sine; 2–8 = tonal; 10+ = aggressive)
• .fmh(N) — harmonicity ratio (the key variable — changes the timbre completely)
• .fmatt/.fmdec/.fmsus — FM envelope (modulation depth decays separately from amplitude)

The non-obvious thing: FM depth envelope independent of amp envelope = the sound brightens on attack and gets purer on sustain. This is the electric piano sound — .fmdec(.2) falls off as the note sustains.

Detune and unison — width and warmth

• Single oscillator: thin, mono, clinical
• Two oscillators, slight detune: chorus/beating, fuller, stereo spread begins
• Many voices, spread detune: supersaw/superpad — the "expensive trance/EDM" wall of sound

In Strudel, detune stacks a copy:

// Chorus/warmth: copy at +7 cents
.add(note("0,.07"))

// Wider unison: copy above and below
.add(note("0,-.07,.14"))

// Slow tape-warble (organic drift)
.add(note(perlin.range(0, .4)))

Craft rule: detune for pads/leads/plucks. Do NOT detune subs — two detuned sines fighting in the low end = phase cancellation and mud. Sub bass stays mono, pitched exactly.

Bass vs. lead: 1–2 voices, ±5 cents max for bass; 5–9 voices, ±15–25 cents for leads/pads.

Sub / body / air — the layering model

A "full" sound is usually three frequency zones working together:

• Sub (20–120 Hz): sine or triangle, no filter, mono, foundation mass. Usually held back in the mix — felt more than heard.
• Body (120 Hz–5 kHz): sawtooth or square with filter shaping. This is the character of the sound.
• Air (5–16 kHz): thin layer of noise, high-passed sample, or bright triangle. Adds shimmer and perceived detail.

// Layer with .layer()
note("C2").s("sine").gain(.8)       // sub
  .layer(
    x => x.s("sawtooth").lpf(1200).lpe(3).lpa(.02).lpd(.4).lps(.3),  // body
    x => x.s("triangle").hpf(5000).gain(.25)                          // air
  )

Common mistake: stacking subs. Two bass voices in the same octave fight each other. Layer frequency bands, not copies.

Saturation — the "expensive" layer

Saturation adds harmonics back to thin signals and glues layers together. It's the difference between "digital" and "analog warmth."

// Soft warmth
.shape(.3)

// Bit-crush for lo-fi / retro character
.crush(8)

// Wave distortion (hard clipping feel)
.distort(.4)

Rules of thumb:

• Light .shape(.1–.3) on pads makes them breathe
• .crush(12–8) on a clean lead = perceived grit without obvious artifacts
• Saturation on a sub kills low end — apply to body layer only, or apply after HPF
• Distortion pre-filter sounds different from post-filter: pre = harmonics get filtered; post = raw grind

Making a sound feel "played not static"

The enemy is the "synth preset no one opened." These are the moves:

1. Filter envelope: even a subtle .lpa(.05).lpd(.3).lpe(2) makes each note have a unique timbral arc.
2. Vibrato with delay: .vib(5).vibmod(.4) — vibrato that kicks in mid-note sounds performed.
3. Velocity modulation: in Strudel, vary .gain(perlin.range(.7,1)) or .fm(perlin.range(2,6)) per note — softer hits feel human.
4. Small pitch drift: .add(note(perlin.range(-.05,.05))) = tape instability, the "alive" quality of old hardware.
5. Release variation: notes stopping at slightly different rates (release(perlin.range(.1,.5))) vs. all cutting at exactly the same moment.

The synthesis-level pro insight (Sound on Sound Synth Secrets): the filter closing on each note is your most powerful "played" signal. A human performer's attack and decay is never the same twice. Model that.

Common mistakes — the short list

• Static filter: .lpf(1000) and done. Sounds like a tone generator. Add .lpe(3).lpd(.3).
• Single oscillator thinness: one sawtooth alone is weak. Add a second detuned copy minimum.
• Detuned sub: phase cancellation. Sub layer must be mono and undetted.
• ADSR defaults everywhere: every synth voice needs deliberate attack, decay, sustain, release — or it sounds like a default preset.
• Over-layering: 6 synth voices fighting in the same frequency band = mud. Three well-separated layers beat six muddy ones.
• Saturation on everything equally: the sub gets killed; the air gets shrieked. Target it at the body layer.
• Ignoring mono check: check layered pads in mono — phase cancellation is invisible in stereo and destroys width when summed.

Strudel synthesis quick-ref

Full filter/effect catalog → [[strudel-effects]]; ADSR modifiers + .vib / .vowel → [[strudel-modifiers]]; GM instruments + built-in synths → [[strudel-sample-library]]; high-leverage moves shortlist → [[strudel-pro-tips]].

See also: [[strudel-arrangement]] [[strudel-harmony]] [[strudel-melody]] [[strudel-groove]] [[strudel-mixing]] [[strudel-genres]] [[strudel-transitions]].

Sources: Strudel Synths Reference · Strudel Effects Reference · Strudel Recipes · Sound on Sound: Synth Secrets series · EDMProd: Subtractive Synthesis · EDMProd: FM Synthesis · Polarity: Classic Synth Sounds · Triple A Beats: Layering Synths · Yamaha: FM Synthesis Basics