https://sfxr.me/

Sfxr, programmed by Tomas Pettersson, and ported to JavaScript by Eric Fredricksen. Forked and improved by Chris McCormick

Parameters and functions provided in jsfxr:

1. Base waveform
2. Envelope
3. Frequency
4. Vibrato
5. Arpeggiation (second pitch)
6. Duty cycle
7. Retrigger
8. Flanger
9. Low-pass filter
10. High-pass filter
11. serialize/deserialize (get settings as text, load settings from text)
12. Buttons (mutate, random, etc.)

This column loads settings

The base waveform at the top of the interface describes what initial oscillator will be used. This decides the original characteristic of the sound.

1. square
2. sawtooth
3. sine
4. noise

We've discussed envelope here. This envelope control doesn't have a “release” parameter, but it has an extra “sustain punch” parameter.

There are four frequency parameters:

1. start frequency
2. min freq. cutoff
3. slide
4. delta slide

Vibrato has two parameters:

1. depth
2. speed

Arpeggiation has two parameters:

1. frequency mult
2. change speed

Duty cycle has two parameters:

1. duty cycle as a percentage
2. sweep as a percentage per second

Retrigger has only one parameter:

1. rate

Flanger has two parameters:

1. offset
2. sweetp

The low-pass filter has three parameters:

1. cutoff frequency
2. cutoff sweep
3. resonance

The high-pass filter has two parameters:

1. cutoff frequency
2. cutoff sweep