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v1.1.2 update: added loop jump hotkeys (v1.1.1) and fixed a crash bug.

RP-8 is a synthesizer and groovebox inspired by Propellerhead Software's classic soft synth, ReBirth RB-338. It has everything you need to make entire tracks: two paraphonic synthesizers, a drum machine, a pile of effects to process your sound, and an integrated song mode sequencer to pull everything together. The audio is lo-fi, 8 bits at 5.5kHz, giving the output a distinctively crunchy sound.

If you're nostalgic for the early era of soft synths, a fan of minimalist computing, an acid squelch connoisseur, or just someone who likes to discover new sounds: I made RP-8 for you.

You can find this cart, including native builds, at https://luchak.itch.io/rp8, or try it out below. Note that this cart works much better natively than on the web - see the Web section under Compatibility Notes below for more info.

Cart #rp8-23 | 2023-11-04 | Code ▽ | Embed ▽ | No License


See the manual, which includes a step-by-step tutorial. RP-8 also has in-app tooltips (enable with T) and a hotkey reference / help screen (view with H).


  • 2023 November 4( (1.1.2) - fix crash on clicking page switch button.
  • 2023 October 10 (1.1.1) - loop jump hotkeys.
  • 2023 September 13 (1.1) - pattern randomizer, copy pattern beginning/end, paste to drum track, bugfixes.
  • 2023 March 4 (1.0) - much more versatile foldback distortion, new demo song, finished docs (now using mkdocs instead of pandoc), tons of sound adjustments and tuning.
  • 2022 September 19 (beta 9) - antialiased oscillators, toned down filter harshness, file menu, "paste sound", tuning changes.
  • 2022 September 11 (beta 8) - vastly improved synth filters, secondary drum sounds, help screen, more hotkeys, song naming, paste-to-control, overdrive bias -> overdrive shape, many tweaks and optimizations. (beta 8b) Updated user guide, next/previous bar hotkeys.
  • 2022 August 6 (beta 7) - overdrive bias control, improved kick decay range, improved hat sound, performance optimizations. (beta 7a) Toasts and UI bugfixes. (beta 7b) Visual improvements, better FM ratio knob scaling, better save compatibility, more hotkeys.
  • 2022 July 21 (beta 6) - lots of constant tweaking and sound adjustments. More filter overdrive, more low end, punchier kick, lots more.
  • 2022 July 17 (beta 5) - removed synth attack knob since it's not being used, reduced low cut on the synth oscillators. (beta 5a) Tweaked overdrive gain compensation. (beta 5b) Fixed page button.
  • 2022 July 15 (beta 4) - removed sample loading and playback, save song files to both desktop and clipboard, drop song file to load, improved synth knob graphics, variable pattern lengths (with awful UI), 2-op FM drum track (control ratio with tune knob, control pitch with chromatic drum sequencing), individual drum track FX bypass, chromatic drum sequencing, second synth oscillator with chromatic sequencing.
  • 2022 April 25 (beta 3) - better handling of changing delay time, level compensation for filter resonance, drum sound tweaks, minor UI improvements, early draft of a manual!
  • 2022 April 16 (beta 2) - fixes to overdrive, output saturation, and the synth filters. Filter resonance goes much higher now, overdrive kicks in more smoothly, and output saturation is gentler.


  • Two vaguely 303-inspired monosynths
  • One vaguely 808-inspired drum machine
  • 16 step pattern-based sequencer with slide and accent steps
  • Pattern mode for real-time tweaking and song mode for recording your work
  • Almost every control on the screen can be automated in song mode
  • Per-synth overdrive insert effect
  • Tempo-synced delay with 16th, triplet, and dotted-16th lengths
  • Routable pattern-controlled lowpass/bandpass filter (like ReBirth's PCF)
  • Master compressor to get the most out of your 8 bits of dynamic range
  • Soft saturation on the output in case you try to get too much dynamic range
  • Audio export
  • Save/load functionality using the system clipboard (doubles as an easy checkpoint feature)
  • Tooltips for most controls (can be turned on/off)
  • Pico-8's PCM output filter is disabled so you can pretend that you have high frequencies

Known Issues

  • Occasional sound dropouts on M1 and M2 Macs, especially when running in the background. This appears to be a PICO-8 issue.
  • Rarely, when re-enabling sequencing on a synth, a slide may not trigger correctly or a non-slide note may be played as a slide.

Compatibility Notes


Most features still work, but pointer lock does not (so large knob movements are difficult), audio recording time is limited, and some browser/platform combinations may have very glitchy audio. On some browsers PICO-8 may interpret pasted documents as keypresses instead of loading them into its clipboard buffer.

Future RP-8 Versions

Future versions may tweak the sound in various ways - if preserving your songs exactly is important to you, please keep your old RP-8 versions around. I'll try to avoid making major changes, though.


... to the #music-sfx channel on the PICO-8 Discord, and @packbat in particular for testing, feedback, discussion, and encouragement. And to @thisismypassword for the essential-to-this-project shrinko8 minifier.

P#109822 2022-04-07 09:01 ( Edited 2023-11-04 19:02)

Post-Release Comments

Oh wow, 1.0! This is very exciting! Congratulations!

P#126617 2023-03-05 15:16

Thank you! It feels very good to put this one in the "released" column. :)

P#126645 2023-03-06 01:04

Great for the 1.0! I'm a big fan of this project :)!

P#127030 2023-03-12 15:21 ( Edited 2023-03-12 15:25)

RP-8 has been featured on Create Digital Music (CDM) -- a music tech site. Congratulations luchak!

P#127127 2023-03-14 14:16

Awesome! I'm happy to see that they posted it. :)

P#127130 2023-03-14 15:45

This is pretty complex, I'll take a look!

P#127521 2023-03-23 18:56

That is seriously impressive.

P#127847 2023-03-30 15:41

Fantastic work!

P#128351 2023-04-09 15:01

bruh, this is more confusing than anything, that usualy means its a good program. so yeah.

edit; finaly figured it out, made this!


P#129436 2023-05-06 02:14 ( Edited 2023-05-22 00:29)

Massive respect and thanks! I found your tool while browsing the Featured collection on my new PowKiddy RGB30 and instantly bought a copy on your itch.io page.

Question, please: Would you be able to add some sort of a "handheld mode" in which the user would move the cursor by joystick and use Z/X as the mouse buttons?

P#136253 2023-10-22 21:44

@AdamJ Awesome! I'm glad you found it.

Unfortunately, a handheld mode is probably not in the making - the cart has very little code space left, and a lot of UI code would need to change for a handheld mode to work well. Save/load also won't really work on handhelds since it uses the clipboard, and there's no way to copy/paste there - this I don't have any good solution for. Song files can easily be too big for cstore(), especially since all the spritesheet space is in use.

If you bought this to use on a handheld, would like a refund, and for some reason need my help to get Itch to give it to you, let me know!

One other idea: if you're willing to settle for an earlier version of RP-8, check out https://www.lexaloffle.com/bbs/cart_info.php?cid=rp8-0 - that's an early beta version released before I decided that I would have to cut console support. d-pad changes selected control, and z/x move knobs up/down and trigger buttons. Not the best UI, but it's at least technically usable!

P#136299 2023-10-24 01:56 ( Edited 2023-10-24 02:13)

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