303_LINE TB-303 emulator

Free TB-303 emulator in your browser

A playable acid bass synthesizer and 16-step sequencer. No download, no sign-up. Make a line, tweak the filter and share it with a link.

Play it

Click steps to program a 16-step pattern. Hold ACC or SLIDE and click a step to accent or slide it, the way the original box does it. Press SHARE to get a link to your pattern.

TB‑303 emulated

Best on desktop with sound on. Some mobile browsers need a tap before audio starts. Turn your volume down before the first run — resonance and distortion can get loud. Keyboard: with the sequencer focused, P runs/stops and R randomizes; Enter or Space toggles a focused step.

How to make an acid line in five steps

  1. Pick a preset from the Presets menu (Starter line, Squelch roll, Slide walk, Offbeat bounce or Minimal stab) and press RUN.
  2. Click steps on and off to change the rhythm. Click a lit step again to change its note.
  3. Turn RESONANCE up and sweep CUTOFF while the pattern plays. That moving, vowel-like squeal is the classic acid sound.
  4. Raise ENV MOD and shorten DECAY to make each note snap. Add a few ACC steps for emphasis and a few SLIDE steps for glide.
  5. Press SHARE and send the link to a friend.

What the controls do

Cutoff
The frequency where the low-pass filter starts closing off the brightness. Low is dark and muffled, high is open and buzzy.
Resonance
Boosts the frequencies right at the cutoff. High settings give the whistling squelch. Turn the volume down first.
Env mod
How far each note's envelope pushes the cutoff upward. More means a bigger "wow" on every note.
Decay
How quickly that envelope falls back down. Short is plucky, long is liquid.
Distortion and reverb
Extra effects added in this emulator to taste.
Wave
Switches between sawtooth (bright, buzzy) and square (hollow, rounder), the two waveforms the original offers.

New to the vocabulary? See the acid glossary. Want the real hardware? See TB-303 clones and reissues.

Frequently asked questions

Is this a real TB-303?

No. It is an original synthesizer built with the Web Audio API in your browser. It is inspired by the TB-303 sound but is not Roland software and does not reproduce the original hardware exactly.

Is it free? Do I need to install anything?

It is free and runs in your browser, with no sign-up and nothing to install.

Can I save or share my pattern?

Press SHARE to copy a link that contains your pattern and knob settings. Anyone who opens the link hears the same line. Nothing is stored on our servers.

Why is there no sound on my phone?

Some mobile browsers only start audio after a tap. Press RUN once, check that your phone is not in silent mode, and turn the volume up gradually.

What do ACC and SLIDE do?

Accent makes a step louder and brighter. Slide glides the pitch from the previous note into that step, which is the squelchy sound the TB-303 is known for. Hold ACC or SLIDE, then click a step.

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