Online Synthesizer

How to play the synthesizer

1. Press Play test chord to check that sound works, and set the Master volume.
2. Play the two-octave keyboard with the mouse or your fingers. Slide across the keys for a glissando; several fingers play several notes at once.
3. Or use the computer keys: the bottom row (Z S X D C V G B H N J M on a QWERTY layout) plays the first octave, the top row (Q 2 W 3 E R 5 T 6 Y 7 U I) the second. The keys follow the physical position, so on AZERTY the bottom row starts with W.
4. Change register with Octave − and Octave +, or with the - and = keys. The lowest key is shown next to Octave (C4 is middle C).
5. Shape the sound with the oscillator, envelope and filter controls below. Changes apply while you play.
6. Have a USB or Bluetooth MIDI keyboard? Press Use a MIDI keyboard and allow access when the browser asks (Chrome and Edge support Web MIDI).

All notes off silences everything at once if a note gets stuck.

The building blocks of the sound

This is a small subtractive synthesizer, the same design as classic analogue synths.

• Oscillator. The Waveform sets the raw tone. Sine is pure and soft, Triangle is a little brighter, Square is hollow and reedy (odd harmonics only), and Sawtooth is bright and buzzy (all harmonics), ideal for strings, brass and leads.
• Second oscillator. Tick Add a second, detuned oscillator to layer another wave. A few cents of Detune (cents) make the two waves beat slowly against each other, which gives the thick, chorus-like sound of vintage synths. Octave offset puts it an octave up or down, and Oscillator 2 level sets the blend.
• Envelope (ADSR). Every note follows four stages: Attack (time to reach full level), Decay (time to fall to the sustain level), Sustain (level held while the key is down, in percent) and Release (time to fade out after you let go). The small graph draws the resulting shape. A short attack with zero sustain sounds plucked; a slow attack and long release sound like a pad.
• Low-pass filter. The Cutoff removes the harmonics above a frequency: lower it to make a bright sawtooth dark and warm. Resonance (Q) boosts the frequencies right at the cutoff for the typical “squelchy” synth sound.

Each note’s pitch is computed in equal temperament from A4 = 440 Hz: f = 440 × 2^((n − 69) / 12), where n is the MIDI note number.

Voices and latency

The synth is polyphonic: up to 16 notes can sound at the same time. When you play more, the oldest note (preferably one already released) is cut to free a voice. A gentle limiter on the output prevents distortion when you play big chords. Audio runs on the Web Audio API in your browser; on most computers the delay between key and sound is barely noticeable, but Bluetooth headphones add their own lag.

Preset ideas

• Pluck: Sawtooth, attack 5 ms, decay 300 ms, sustain 0 %, release 200 ms, cutoff around 2 kHz.
• Pad: two sawtooths detuned by 10 to 15 cents, attack 800 ms, sustain 80 %, release 1.5 s, cutoff low.
• Organ: Sine with a second oscillator one octave up, attack and release near 0, sustain 100 %.