Every synthesized sound on this planet starts with an oscillator. Here's what each control actually does, and why it matters.
A waveform is a picture of how air pressure changes over one cycle of the sound. Different shapes produce different tones. Sine waves are the purest — a single frequency with no overtones, sounding like a flute or tuning fork. Square waves contain only odd harmonics and sound hollow, like a clarinet or classic 8-bit video game. Sawtooth waves contain every harmonic and sound bright and buzzy — the foundation of string and brass synth sounds. Triangle waves are soft and mellow, like a warmer sine. The Custom shape lets you draw your own waveform; the tool converts your drawing into a real mathematical wave via Fourier analysis. Pluck is a different beast entirely — a physical model of a plucked string (Karplus-Strong algorithm) that sounds remarkably like a real guitar or harp.
Every real instrument has an envelope: a piano note starts instantly (fast attack), decays quickly to a sustained ring, then fades when you lift the key. A bowed violin has a slow swell (slow attack), a steady hold, and a gentle release. The four ADSR sliders recreate any of these shapes. Attack is how long the sound takes to reach full volume. Decay is how long it takes to fall from full to the sustain level. Sustain is the hold level while you're still holding the key. Release is how long it fades out after you let go. Setting attack=0, sustain=0, decay short = a plucky stab. Setting attack long, sustain high, release long = a pad that swells and lingers.
Every waveform except a sine contains multiple harmonics (frequencies stacked on the fundamental pitch). A filter removes some of them. A lowpass filter keeps lows and cuts highs, making the sound darker and warmer. A highpass does the opposite. A bandpass keeps only a narrow frequency range, sounding nasal or telephone-like. The cutoff slider sets where the filter starts acting. Resonance boosts the frequencies right at the cutoff point — low resonance is subtle, high resonance creates the classic "wah" or whistling character heard in every acid house track ever made.
A Low-Frequency Oscillator is a second oscillator that runs below hearing range and is used to modulate another parameter. In this tool, the LFO modulates pitch. A slow LFO (0.3 Hz, small depth) produces gentle vibrato — the wobble in a singer's voice. A faster LFO (5 Hz, moderate depth) produces a classic tremolo or chorus effect. A very fast, wide LFO creates sirens, warbles, or alien warp sounds. The rate slider controls how fast the LFO cycles; the depth slider controls how much it affects pitch.
Subtractive synthesis (waveforms + filters) can make almost every instrument sound, with two exceptions: bells and electric pianos. That's because bells and metallic percussion have inharmonic partials — frequencies that aren't simple multiples of the fundamental — and you can't make those by filtering a sawtooth wave. You make them with Frequency Modulation: a second oscillator (the modulator) modulates the frequency of the main oscillator (the carrier) at audio rate. The ratio slider sets the modulator's pitch relative to the carrier — whole-number ratios (2, 3, 4) produce harmonic results (electric piano, organ), non-integer ratios (2.3, 3.7) produce bell-like, metallic, dissonant timbres. The amount slider controls how intensely the modulator affects the carrier — zero is no effect, high values create radical timbre changes and inharmonic chaos. This is how every Yamaha DX7 patch you've ever heard works.
Press Record to capture everything that plays. The tool uses the browser's MediaRecorder API to capture audio, then re-encodes it to uncompressed WAV when you stop. WAV files work on every device, every audio editor, and every DAW — pristine quality with no compression artifacts, at the cost of larger file size than MP3. You can import the file into GarageBand, Audacity, Ableton, FL Studio, or any editor and treat it as a raw synth take.