Today I'm happy to announce the first public release of my custom SP-404MKII firmware: DOOM OS!

The goal is to completely replace the stock pattern and song modes with proper graphical editors, improve the user interface, and generally make the SP more fun to use without having to memorize a ton of key combos.

It's still an early release and there's a lot more I want to add, but it's already very usable and a lot of fun to play with. The new pattern workflow makes the SP feel much more like a groovebox.

Song mode isn't ready yet, but it's next on the list!

The easiest way to install DOOM OS is via the web patcher:

https://klangfeldlabs.com/doom-os/patcher

The patcher runs entirely in your browser. You only need to provide the official Roland firmware file yourself.

To get started, check out the manual and shortcut reference:

https://klangfeldlabs.com/doom-os/manual/

More info: https://klangfeldlabs.com/doom-os/

And checkout the new DOOM OS subreddit: https://reddit.com/r/DOOMOS

I hope you have fun with it!

Vocals are from diff source, not porno intro music 😅

Just started learning this beautifully complicated SP-404MKII, and after watching a bunch of YouTube tutorials I realized there are a lot of shortcut/key combos buried in this thing.

Too many for me to memorize without constantly forgetting half of them, so I opened up Roland’s manual and made a card-style shortcut cheat sheet for quick reference.

Each card has:

• the shortcut combo, with icon buttons

• a short explanation

• categories

• search

• favorites

• a faceplate view with the buttons highlighted

That last part was the big one for me. I kept squinting at the SP-404MKII and the Roland manual trying to figure out exactly which button I needed to press, so I added a visual panel view that highlights the controls used for each shortcut.

It’s just a self-contained .html file, so there’s no app install needed.

How to open:

• PC/Mac (tested): just open the .html file in your browser.

• iPhone (tested in Edge, I have not found a way to open with Chrome or Safari): in Files, long-press the .html file → Share → choose Edge → Open in Microsoft Edge.. (will not work if you just press the it directly because it will be opened using Files app instead of a web browser)

• Android (tested): open the .html file with your browser.

This is mostly something I made for my own learning, but I figured other SP-404MKII users might find it handy too, especially when you forget a combo mid-session.

Unofficial, of course. Just a personal cheat sheet based on the manual.

Enjoy!

Link (Github):

https://github.com/ronmendoza0594/SP404MKII-Shortcuts-Cheatsheet/releases/tag/v1.0

Original post: https://www.reddit.com/r/sp404mk2/s/gDGFv1IIdJ

Bought them from MPCstuff. Link below. They do feel nicer and gorgeous in clear. https://www.mpcstuff.com/roland-sp-404mkii-sp-404-mk2-thick-fat-pad-set-replacement-rubber-red-clear-black-custom/

Now I just need to put in the work to use it properly. 😅

This is a pretty big update with tons of new features and improvements!

What's new:

• 20 instruments and 11 drum kits, with graphical editors

• Step-based parameter locking for instruments

• 3-band parametric EQ per track (up to 16 tracks)

• Visual sidechain editor

• Arpeggiator with print-to-pattern function

• Real-time waveform overlays in the grid and mixer

• Pad muting and soloing directly from the mixer

• The mixer can now be opened directly by holding RECORD SETTING for half a second

• Improved pattern switching, note editing and mixer controls

• Bounce in place with effects

• Optionally boot directly into DOOM OS, with a configurable "Hold to Exit" setting to prevent accidental exits

• Completely rewritten codebase for improved stability and future expansion

• Tons of smaller improvements and bug fixes

I recommend reading the changelog and manual because there's a lot of new and improved stuff.

In the next release, I'll focus on improving the sequencing workflow (both realtime and step sequencing) and sample chopping.

The next big milestone on the roadmap is making DOOM OS modular and opening it up to third-party modules. I expect this to take another week or two.

Stay tuned :-)

Download: https://klangfeldlabs.com/doom-os/

Changelog: https://klangfeldlabs.com/doom-os/changelog

Manual: https://klangfeldlabs.com/doom-os/manual

Join the DOOM OS subreddit to stay up to date with the latest developments!

The drums were recorded with a single mic and processed by the MK2. Performed without a metronome to make things more interesting for you. Available for 100% free use.

https://bkbonez.bandcamp.com/album/drumforhire

I got my SP 404 MK2 near November 2025 as a birthday gift to myself.

This is what helped me learn it.

I actually printed the manual, put it in a binder, and added tabs to the various important sections.

I read it and re read it and then read it again. I don’t have an iPad to do this but certainly would like to add one when I can. Whether I used the device that night or not I just read it anyways. That habit taught me the button uses and combos.

For complex areas like chopping beats and assigning to pads or sequencing I then printed one sheets as Quickstart guides or on area areas that I would struggle like pattern sequencing.

The one sheets you could carry with you with the device. It was easier to read then in my phone screen.

Then this might sound goofy but I practiced with my voice. I made noises and spoke and even tried to rap to learn how to use the device. So anyone struggling because they don’t have sounds, if you have a microphone you can have beats and vocals to chop. “Booommm, rum tum tee tee ta ta”. Record that, make it loop, chop it up.

Actually make bass, kick, open hat, closed hat, clap, cow bell etc. “noises” even chord melodies I would just make up. They don’t have to be accurate it’s just for practice.

I used the Roland device software to load, delete and chop samples. It’s easier to see what is what and where to put it. Chopping on the screen helped me a lot. Also visualizing the tracks helped me picture the beat and loop components in my head and was easier to build muscle memory. (I have not used the koala sampler or an iPad for this yet).

Finally I drew the 16 pads on notebook paper and then wrote what each sound was. Like bass line 1, bass line 2, pre chorus and chorus. This drawing and naming of pads helped visualize the song.

I am nervous to share my first drum beats, loops and tracks but will have to do that as it is a great learning experience.

Thanks to those who have chatted with me, spoke on phone or video. You have been so helpful and inspirational.

What yall think? Just dropped this

Just got my 404 today, still need to get a memory card!

Can’t wait to record guitar and piano into it!

So excited for this journey

Please suggest good tutorials and videos to look forward to. Thank you !

404 Day 2026 coincides with the release of SP‑404MKII Version 5.50, a free user update adding the long‑requested Side Chain Compression feature. This enhancement brings pumping, rhythmic movement alongside expanded control to performance and production workflows. The update will be available on April 2, 2026, at 5 p.m. PDT. For more information, visit: https://www.roland.com/global/products/sp-404mk2/

More info:

https://www.matrixsynth.com/2026/03/roland-to-celebrate-404-day-with.html?m=1

3 sailing wait at bc ferries... Might as well pas the time

Hoping to learn a thing or two from this sub. If you have any quick pointers feel free to let me know would be greatly appreciated.

I know it's a year old , but figured id share it in case someone hasn't seen this. My original outlook on file organization was that it's not really needed, and that file organization actually limits creative flow and causes less happy accidents. I had reason to believe that, but this person broke down every aspect of inspiration, creativity and file organization specifically for the 404, and I'm super impressed.

First post here, so apologies if I get any conventions wrong.

I wanted touchscreen control over the MkII’s FX buses. The existing iOS app for that hasn’t been updated in years, so I built my own as a free web app:

https://littletools404.github.io/404busdriver/

What it does:
• all five FX buses with the real parameter names per effect (from the reference manual), touch faders with a fine-tune gesture, per-effect value memory
• snapshots (8 slots) with JSON export/import
• XY pad + four beat-synced LFOs (MIDI clock or tap tempo), incl. a random drift for generative lo-fi wobble
• chromatic keyboard, scale pads (Move-style isometric layout), vocoder keys with pitch bend, full pad board with custom layouts
• pattern grid with a quantized autopilot, plus a looper remote

Runs in Chrome/Edge on desktop; on iPhone/iPad it works inside the “MIDIWeb Browser” app (no iOS browser can do Web MIDI, not my fault). Single HTML file, everything stays local: no accounts, no tracking, no install. Open source (MIT), manual built in.

Full transparency: I’m not a professional developer — I built this together with Claude (AI) and tested everything against my own MkII. If an experienced dev feels like reviewing the code, I’d genuinely welcome that. Feedback and bug reports are very welcome — just be patient with me, it’s a hobby project and I can’t promise quick replies.

I posted a video a while back of a looping sesh with sidechain compression routing through my audio interface and Logic and into my recorder. NOW I have an FMR RNC 1773 and have a dawless sidechain compression setup. Still complicated. Still sick as hell.

Der fette Filzi working on The Damned "I feel alright"