Online Synthesizer

What this online synthesizer is

This page is a small synthesizer you can play in your browser. It has four waveforms, a detune control that thickens the sound, a low-pass filter with resonance and a sweep, and a four-stage envelope. A four-octave keyboard from C2 to C6 lets you play it with a mouse, a touch screen or your computer keyboard. Nothing needs installing and no account is required.

It is a subtractive synthesizer, the classic design in which a raw, bright sound is shaped by removing parts of it. All the sound is generated in your browser using the Web Audio system, and no audio files are downloaded.

Waveforms: the raw sound

Every note starts as a repeating wave, and the shape of the wave decides its tone. The four choices here are the traditional building blocks of synthesis:

• Sine. A single pure frequency with no overtones. It sounds smooth and flute-like, and it is the quietest and simplest.
• Triangle. Close to a sine, with a few weak odd overtones. It is soft and slightly hollow.
• Saw. Contains every overtone, falling in strength as they rise. It sounds bright and buzzy and is the usual starting point for strings, brass and leads.
• Square. Contains only the odd overtones. It sounds hollow and reedy and is common for basses and retro game sounds.

Waves rich in overtones give the filter more to work on, which is why the saw is the default.

Detune: making the sound thicker

Each note is made from two oscillators playing the same pitch and waveform. The Detune slider moves one slightly sharp and the other slightly flat, by a few cents, where a hundred cents make one semitone. The two waves drift in and out of step, which makes a slow shimmer that sounds wider and more alive than a single oscillator. Zero detune gives a clean, single sound, and high values start to sound out of tune.

The filter: cutoff, resonance and sweep

The filter is a low-pass filter. It lets low frequencies through and cuts high ones, and the cutoff is the point where the cutting starts. With a low cutoff, a saw wave sounds dark and muffled, and as you raise the cutoff it gets brighter. The slider is shown in hertz and moves in steps that sound even to the ear.

Resonance boosts the sound right around the cutoff. A little adds character, and a lot gives a pointed, whistling edge, so turn it up gradually. Filter sweep makes each note start with the filter wide open and then close down to the cutoff you chose. That quick move from bright to dark is behind many classic plucks and basses, and the higher the sweep, the wider the move.

The envelope: attack, decay, sustain and release

An envelope describes how the volume of a note changes over time, in four stages:

• Attack. How long the note takes to reach full volume after you press the key. A short attack is punchy and a long one fades in.
• Decay. How long it takes to fall from full volume to the sustain level.
• Sustain. The level the note holds at while you keep the key down, as a percentage of full volume.
• Release. How long the note takes to die away after you let go.

A piano-like pluck has a quick attack, a medium decay, zero sustain and a short release. A pad has a slow attack, high sustain and a long release. Both sound very different even from the same waveform.

Playing with a mouse, touch screen or keyboard

• Mouse. Press and hold a key. Hold the button and drag across the keys to glide from note to note.
• Touch screen. Touch and hold keys, using several fingers for chords. Swipe the keyboard sideways to reach other octaves.
• Computer keyboard. The bottom row, Z X C V B N M, plays the white keys of one octave, with S D G H J as the black keys. The top row, Q W E R T Y U I O P, plays the octave above. Each key shows its letter.
• Keyboard navigation. Press Tab to reach the keys, use the arrow keys to move, and hold Enter or Space to play the focused key.

The synthesizer is polyphonic, so you can hold as many notes as you can press, and each one runs its own envelope.

The four presets

Lead is a bright detuned saw with a quick sweep, made for a melody. Pad is a soft, slow saw with a long attack and release, which suits held chords. Bass is a square wave with a low cutoff and some resonance, best played in the lowest octaves. Pluck has no sustain, so each note rings out and dies away even while you hold the key.

The presets are only starting points. Move any slider after choosing one and the preset highlight clears, so you can see you have made your own sound.

Beginner exercises

1. Compare waveforms. Play the same note on each of the four waveforms and listen for the difference in brightness.
2. Open the filter. Hold a note on the saw wave and slowly raise Cutoff. Then turn Resonance up and repeat.
3. Change the envelope. Set Attack to about 800 ms and Release to about 1500 ms, and play a chord. Then set both to the minimum and compare.
4. Build a pluck. Set Sustain to 0, Decay to about 300 ms and Filter sweep high, then play a short melody.
5. Thicken it. Raise Detune to about 20 and play a held chord for a wide, shimmering sound.

What an online synthesizer is good for

An online synthesizer is a quick way to learn how sounds are built. It suits students who want to hear what a filter or an envelope does, songwriters sketching a bass, lead or pad, and anyone curious about electronic sound. Try the virtual theremin for gliding pitch, the online organ for another way of mixing tones, or the music maker to put sounds into a loop.

Online synthesizer versus a hardware one

Hardware synthesizers have knobs under your fingers, many more waveforms and filters, modulation from low-frequency oscillators, effects and weighted or velocity-sensitive keys. Studio synths can store hundreds of sounds and connect to other equipment with MIDI.

This one has a single oscillator pair, one filter and one envelope, and every note is played at the same strength. It is a good way to learn the basic ideas and make simple sounds, but it is not a replacement for a full instrument or for a software synthesizer built for production.

Limitations of this version

• Each note uses two oscillators with one waveform. Mixing different waveforms is not offered.
• There is one low-pass filter and one envelope, which shapes volume. There is no low-frequency oscillator and no effects.
• A new waveform applies to the next note, not to notes already sounding.
• Every key press has the same strength, and there is no MIDI input or recording.
• Loud settings, such as high resonance with a low cutoff, can be sharp. Start with the volume low.

Common problems and how to fix them

• No sound. Browsers keep audio off until you interact with the page, so press a key first. Then check the volume slider, your device volume and the tab's mute icon. On an iPhone, also check that the silent switch is off.
• The sound is very quiet or muffled. Raise Cutoff, and check that Sustain is not at 0, which makes held notes fade away.
• The note stops while I hold it. Sustain is at 0 or very low. Raise it for a held tone.
• The sound is shrill. Lower Resonance or Cutoff.
• The letters play the wrong notes. Check the octave setting. The layout follows the physical position of keys, so on a non-US keyboard the letters on your keys may differ from the labels on screen.