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Sound lab: synthesizer, sampler, sound design

About this app

A polyphonic synthesizer as a signal chain of source, filter, VCA and effects: subtractive, FM, wavetable, sampler and granular, with envelopes, LFOs and a modulation matrix. A 3D waterfall spectrogram shows live how the filter cuts away overtones, or how a sample played an octave higher becomes twice as high and half as long. Eleven sound design recipes explain why it sounds that way.

The signal chain of a synth

A synthesizer makes sound in a chain: a source provides a waveform, a filter shapes its harmonics, an amplifier (VCA) controls loudness through an envelope, and effects colour the result. In subtractive synthesis a filter removes harmonics from a rich waveform such as a sawtooth. In FM synthesis one sine wave modulates the frequency of another, creating sidebands at f_c ± n·f_m. A sampler plays recordings and transposes them by a factor of 2^(n/12).

What the app shows

The Sound Lab is a polyphonic synth with subtractive, FM, wavetable, sampler and granular modes, plus filter, envelopes, two LFOs, a modulation matrix and effects. A 3D waterfall spectrogram shows at a chosen tap point (source, filter, VCA, output) what happens to the harmonics: how a filter cuts them away, or how a sample played an octave higher becomes twice as high and half as long. Eleven sound-design recipes such as acid bass, supersaw pad, FM bell, kick or granular cloud load ready-made settings and explain why they sound the way they do.

Try it yourself

Play with the on-screen keyboard, your computer keyboard or a MIDI controller. Load a recipe, then change single controls and watch the spectrogram, for example while turning cutoff and resonance. In the sampler you can record up to 5 seconds from your microphone and transpose it; the recording stays in your browser.

Frequently asked questions

What does resonance do on a synth filter?
Resonance boosts the frequencies right at the cutoff while the filter keeps attenuating the harmonics above it. The spectrum shows a peak at the cutoff and the sound becomes sharper and more nasal. Sweep the cutoff with an envelope at high resonance and you get the squelchy “acid” bass sound; many analogue filters start to oscillate on their own at maximum resonance.
How is FM synthesis different from subtractive synthesis?
Subtractive synthesis starts from a harmonically rich waveform such as a sawtooth or pulse and shapes it by filtering harmonics away. In FM synthesis one sine wave (the modulator) varies the frequency of another (the carrier), which creates sidebands at f_c ± n·f_m whose strength depends on the modulation index I (Bessel functions J_n(I)). Integer frequency ratios give harmonic tones; non-integer ratios such as 1 : 1.4 give inharmonic, bell-like ones.
Why does a sample get shorter when you pitch it up?
A basic sampler changes pitch by playing the recording faster or slower, by a factor of 2^(n/12) for n semitones. One octave up (+12 semitones) doubles the frequency and halves the duration, and the formants move too, which is why a pitched-up voice sounds like a chipmunk. Granular synthesis and time-stretching decouple pitch from duration by playing short grains at their own read speed.
What can I try out in this app?
You play a polyphonic synth with the on-screen keyboard, your computer keyboard or a MIDI controller and switch between subtractive, FM, wavetable, sampler and granular modes. Filter, envelopes, two LFOs, a modulation matrix and effects are all adjustable, and a 3D waterfall spectrogram shows what happens to the harmonics at a chosen tap point (source, filter, VCA, output). Eleven recipes such as acid bass, FM bell or granular cloud load ready-made settings and explain them, and the sampler can record up to 5 s from your microphone; the recording stays in your browser.

Subject: Music (Gymnasium)

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