https://sfxr.me/

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

First point: make sure that you select 44k and 16 bit in the column on the right for maximum sound quality (unless you are deliberately going for the old-school vibe).

The concept is to pass the output of a basic oscillator through an envelope and a few effects to generate a sound.

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.)

The random button randomizes all of the parameter settings, likely creating a totally new sound.

This column contains buttons for presets, which load parameter settings for sounds that correspond to the labels. After loading them, you can adjust the parameters to customize the sound.

The mutate button slightly changes all of the parameter settings, creating a variation of the previous 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