Effect 12 of 15 · Pedals
Tremolo: the volume, moving
The simplest effect on the board. An oscillator turns the volume down and back up, again and again.
Play it alone
Signal into the board
Use headphones. With speakers, a microphone hears the board’s own output and sends it round again: that loop is feedback, and it howls. Turn the output volume down before you press Start.
The test signals are synthesized by this page, sample by sample. Your instrument is asked for only when you press Start with “Your instrument” chosen, with the browser’s echo cancellation, noise suppression and automatic gain control switched off.
Clipping: the output reached full scale. Turn a level down.
- Sample rate
- not started
- Processing latency
- not started
- Output latency
- not started
- Input latency
- not started
- Reported total
- not started
Browser audio has latency: you hear each note a little after you play it. These are the browser’s own figures and they leave things out.
The tremolo, alone
In, this one pedal, out. Drag a knob sideways, or focus it and use the arrow keys or the wheel. The whole board has the rest.
Tremolo
Rate5 HzDepth60%ShapeSine
The signal
What it does to the signal
Tremolo is a change of loudness that repeats. Nothing happens to the pitch or the tone of the signal; only its level moves.
The signal passes through one gain. An oscillator moves that gain between 1 and 1 minus the Depth: at 60%, between full level and 40% of it. Rate is how many times a second it goes down and comes back.
Shape is the waveform of the oscillator. A sine glides down and up. A triangle moves at a constant speed and turns round sharply. A square switches between the two levels and stays at each for half the time. The oscillator is one cycle of the wave written into a one-second buffer and looped, so that it reaches exactly +1 and −1, and it passes through a 120 Hz low-pass on its way to the gain, so that the square wave’s jumps take a few milliseconds and do not click.
General definition: Wikipedia, “Tremolo (electronic effect)” (revision 1052496149, read 2026-09-28). Everything on this page about how this pedal works describes this page’s own code. It is built from standard Web Audio nodes.
The graph
The graph, drawn.
audiocontrol: moves a setting, is never heard
The dashed line is a control signal: the oscillator moves the gain and never enters the signal path.
The knobs
Every knob, in real units.
| Knob | Range | Starts at | What it changes |
|---|---|---|---|
| Rate | 1 Hz to 15 Hz | 5 Hz | How many times a second the volume dips. |
| Depth | 0% to 100% | 60% | How far the volume dips. The gain swings between 1 and 1 minus this share. |
| Shape | Sine / Triangle / Square | Sine | The waveform of the oscillator that moves the gain. It passes through a 120 Hz low-pass first, so the square’s edges are fast but are not clicks. |
Measured
What the test measured
Rendered offline, then measured
- Switched off and rendered over 48,000 samples of the plucked-string signal, the output was identical to the input in every sample, and the pedal was not in the graph. [as described]
- Rate 5 Hz, Depth 60%, a steady 1 kHz tone in: the output’s level swung between 99.9% and 40.1% of the input’s. Depth 60% means between 100% and 40%. [as described]
- The level fell through its mid-point 13 times in 2.5 seconds, 200.0 ms apart on average: 5.00 times a second. [as described]
- With Shape on Square and Depth at 100%, the level was within a tenth of fully on or fully off for 96% of the time, and its lowest point was −174 dB below its highest. [as described]
Rendered in an OfflineAudioContext at 48,000 Hz in Chrome/154.0.8037.58, 2026-09-29 01:07 UTC. The test is work the page’s builder ran, not something your browser does when you open this page.
Limits
- Mono. It cannot move the sound from side to side.
- Changing Shape starts a new oscillator, which begins at the start of its cycle.
Where it goes in the chain
Late, after the drive and the other modulation. GuitarPlayer’s guide to pedal order places modulation towards the end. Before a drive pedal, a tremolo changes how hard the drive is hit and so how much it distorts, which is a different effect from changing the level of the result. The whole order, and the reasons, are on the signal chain page.
Method
What is computed, and what is read.
Computed here, nothing fetched
Every sound on these pages is computed in your browser by the Web Audio API: 9 of the 15 pedals are graphs of the engine’s standard nodes, 5 are AudioWorklet processors, the wah is both, and the 3 test signals are synthesized sample by sample. No recording is loaded and no data feed is read. The one request the board’s own scripts make is for their AudioWorklet module, a file on labs.llc; the pitch detector is the one the Tuner uses.
Every effect was rendered offline with a known signal and measured: 73 of 73 checks came out as described. Nothing was tested on a real instrument or audio interface, only one browser was used, and nobody listened: the tests measure numbers, not tone. The method, the table of checks and what the latency figures mean are on the about page.
Sources
The W3C Web Audio API 1.1 and Media Capture and Streams specifications (W3C Document License); RFC 9110 and RFC 3986 for the share link’s fragment; GuitarPlayer’s guide to pedal order, quoted briefly; Wikibooks, “Guitar/Effects Pedals”; and each effect’s English Wikipedia article at a named revision (CC BY-SA). All read 2026-09-28; none is fetched by the page.
What happens to what you play
Audio from your input goes into the audio graph and out to your output device, and nowhere else: it is not recorded, stored or sent. Presets and the board as you left it stay in this browser’s local storage. A share link carries the board after the #, which browsers do not send to servers.