303Gen – 303 acid loops generator
26 comments
·August 6, 2025errozero
lelandfe
Sick. If you throw this up on GitHub/whatever I’ll PR a more responsive layout for mobile
blackhaz
This is amazing. Thanks for making it.
bityard
Oh this is lovely! I love the 303, played with ReBirth a LOT and built several x0xb0xes back in the day.
About half of the patterns it generated were something I could listen to for a while. Makes me want to get back into electronic music again.
driggs
Not only does this sound excellent, with three great TB-303 synth engines with a colored delay, but it's very musical. The three patterns are locked to a common scale/mode, they autogenerate with compatible and often interleaving polyrhythms, and the "instruments" - bass, lead, drone - spawn with complimentary defaults.
As a longtime synth nerd, it still amazes me to see beautiful tools like this running in a web browser.
Excellent job!
alisonatwork
I agree that it's neat to have software synths that can run in the browser nowadays, but this isn't really a good TB-303 emulation. The accent doesn't have a slow enough attack to create the "wow" effect, which is a fundamental aspect of getting any random acid line to sound properly 303ish. Not to take away from what it is, but for a synth that has been cloned and emulated as often as the TB-303, your description is overselling it a bit.
quatonion
Come now. Being kind is also a thing, and I think it sounds more than acceptable.
quatonion
It's brilliant. Love it. I want to know more about the generation, it looks very well thought out. Worth an article in itself.
nzoschke
Fun. I love the UI style.
See also the Endless Acid Banger:
https://www.vitling.xyz/toys/acid-banger/
And happy Acid August!
Every year we celebrate the 303 with a club night in SF.
pdntspa
It would be cool if this showed the patterns in a visual manner that I could copy into my 303 VST of choice
kookamamie
When clicking Regenerate, it would be great if the sequence kept playing if Play was active at that time.
ZFH
cries nostalgia tears in Propellerhead Rebirth
Thanks.
serpent
Lovely! Is the source code public?
errozero
No, but the timekeeping part of it is. I put that code into a small library to use in my music apps: https://github.com/errozero/beatstepper
efields
What would be the level of effort to get some midi transport controls and BPM sync in here, now that browsers support MIDI to some degree?
mtts
Everybody needs a 303.
leptons
I'm a little sad that the 303 sound had such a short-lived and niche life. In the 90's it seemed to me like it was the first instrument that could challenge the hegemony of the electric guitar. It was so versatile - the sound is bouncy, melodic, and had some real "growl", all at the same time.
mxuribe
Also within ungoogled chromium, upon hitting the "stop" button, it seems to keep playing either an additional lower-volume track, or some long delayed echo....but hitting the "stop" button several times eventually stops playback. Even still, the concept is pretty neat!
Hey, I made this a few years ago. I'm suprised to see it posted here today. It was never finished and I was meaning to add a polyfill for the missing cancelAndHoldAtTime function for Firefox. Edit: I've just hacked in a quick polyfill