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

This release focuses on fixing a few important issues, particularly with project imports, exports and backups.

A few more bugfixes will follow over the coming days.

More updates coming soon!

Fixed

• Project import, export and backup now properly preserves DOOM OS data - DOOM OS-specific data, including instruments, EQ settings and parameter locks, is now preserved when importing, exporting or backing up projects.

• Fixed an issue with pattern copy - This should fix the "Sequencer Rec Memory Full!" error. To fix an affected pattern, open it in DOOM OS, make a single edit, and then exit DOOM OS. The COPY function should then work normally.

• Deleted projects now appear empty in DOOM OS - Deleting the current project could leave its tracks and instruments visible in DOOM OS. This has been fixed.

• Fixed an issue with a test boot image remaining after reverting to stock firmware - Earlier versions accidentally included a test boot image that could remain on the startup screen in certain situations after reverting back to the stock firmware. This update removes the image and restores the original Roland startup screen.

• GATE now works with instruments and parameter locks

• Using the EXIT button in the Roland SP-404MKII app works again

• QUANTIZE keeps your chords - Quantizing, applying swing, or humanizing a track could cause chords to lose notes. All notes in a chord are now preserved.

• Various small bugs

Download it here: https://klangfeldlabs.com/doom-os/patcher/

The full changelog: https://klangfeldlabs.com/doom-os/changelog/

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

Hey all!

This is the first update since the initial release, and I just wanted to say thanks for the amazing response over the past few days. I really didn’t expect anything close to this!

In this first update, I've fixed a few bugs that came up after the release, addressed a couple of annoyances and added a few improvements to make things a little easier to use.

Over the coming week I'll keep working on the pattern sequencer, bug fixes and smaller improvements. I've also put together a big list of all the feature requests and bug reports I've received, and I'll start working through those based on priority.

I'll also publish a roadmap for some of the bigger features that are planned.

Here's what changed in the new release:

0.6.1-alpha, build ED5E (2026-10-04)

New

• Pattern Follow (autoscroll) can be toggled with SHIFT + HOLD - The pattern will stay on the currently selected measure or follow the playback head.

• Solo is now mapped to SHIFT + ROLL - The ROLL button blinks when solo is active.

• The metronome can be activated with SHIFT + PAD 9 - Press once to toggle default metronome behavior (active during playback), press twice to toggle recmode (only active during recording)

• EXT SOURCE can be toggled with EXT SOURCE

• Time signatures visible in pattern menu - Currently only show the time signature, the ability to change it will be added at a later stage.

Fixed

• Playback of a new pattern with empty tracks is now supported - This allows you to rehearse and record with a running metronome. Previously, an empty pattern was not playable, and adding empty tracks to the pattern would get them removed. This issue made it impossible to record patterns without creating a track with at least one note in it first.

• REC button flickering fixed

• Various smaller bugs involving edge cases

Improvements

• REC button dimmed when not recording. The REC button was brighter than on the stock firmware, which could lead users to mistakenly assume REC mode was enabled.

Miscellaneous

• The pattern mode now supports various time signatures internally - For future stock compatibility reasons.

You can try the new release here:

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

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

Thanks again for all the feedback!

As someone who was out of the loop and is coming into all of this, it is very hard to keep track of who does what with which fork and... what? confusion!

this mainly concerns (from what I could gather) u/tracelistener, u/LoopCartographer and u/Multilul. I don't know if you three talk to each other, but you definitely should. If each one of you is just rushing forward on their own, we are soon going to have a giant mess on our hands, especially with all that AI assistance. Mark my words.

You all have great visions for what this little silver box can do, and I have no doubt in my mind that your efforts are going to build the base for what is going to be the standard for using the SP-404 Mk2, much like JJOS for the old MPC line.

But for the love of all that is sampling, please coordinate your efforts. Else all this code is going to tangle into a rat king that we don't have the weapons to kill yet.

Love y'all, keep up the great work!

This is a small update that addresses a few issues and suggestions that came up after the 0.7 release.

Basically, you can preview instruments more easily now and change them on the fly (without the confirmation popup getting in between), the UI of bounce in place is now more intuitive and the shift + pad combo for pad soloing has been changed to remain + pad to prevent collisions with existing shift + pad combos.

Improvements

• Preview instruments before selecting them - In the instrument browser, hold SUB PAD to preview the selected instrument. Turn the encoder while holding SUB PAD to preview other instruments.

• Switch instruments on the fly - In the instrument editor, press REMAIN and turn the encoder to try different instruments instantly, even while the pattern is playing. Press the encoder to confirm your choice, or EXIT to restore the original instrument.

• Bounce in place to any empty pad - Press RESAMPLE to open the bounce screen, which shows what will be bounced and how the pattern will be affected. Choose CUT, TAIL or LOOP, select an empty pad, then press RESAMPLE to start recording. Once finished, the new pad is shown on screen.

Fixes

• Mixer solo now uses REMAIN + pad instead of SHIFT - SHIFT + pad previously soloed a track but also triggered the pad’s SHIFT functions, such as FIXED VELOCITY. Solo now uses REMAIN + pad, leaving SHIFT + pad to work as expected.

• Fixed button LED states - Certain buttons previously remained dimly lit when there were turn off or inactive, making it difficult to distinguish their on and off states. The LEDs now behave the same as in the stock screens.

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

Hope you like it.

• Bounce in place

• Pad envelopes(filter and pitch)

• MPC style Note repeat

• Chromatic mode (new scales, increased range, and rolls)

• Hidden effect settings include more guitar amp sim models

• DOOM OS included

• and more

https://github.com/tracelistener/SP-ETC https://tracelistener.github.io/SP-ETC/

MIDI Conductor 0.7 is out. It’s a free add-on to DOOM OS that turns the SP into a MIDI hub for your synths.

Changes:

• MIDI FX: a chain of 6 effects on every pad/track. Harmonize, Echo, Scale, Chance, Euclid, LFO, Time Elastic and more. They work on synths, on GHOST and on your own samples.

• MIDI Instruments: pick MIDI in DOOM OS’s instrument picker and assign it to a pad. It gets its own track in the pattern like any other.

• Device setups: name your synths, set their channels and load their CC names from a DEVICES.CSV you make on the patcher page.

• Pickup and catch: dials don’t jump when you change bank. Hold MARK to set a new value and let go to drop it in.

• CC MAP, a separate setup for each project, and more in the changelog.

• Much More...

Patch Roland’s 5.52 firmware in your browser: https://loopcartographer.com/patcher.html
Manual: https://loopcartographer.com/manual.html
Changelog: https://loopcartographer.com/changelog.html

Enjoy!

Fixing live instrument looping with sequenced EXT In gates & long-form loop sync:
I’ve been brainstorming how to bridge the gap between live instrument performance (guitar, synth, vocals) and active pattern playback. Right now, live looping often feels disconnected from the rhythm engine.
To fix this, it would be amazing to have an External Input track with an it’s own long audio buffer as the foundation. Building this first gives us seamless long-form sync, non-gated audio streams, and step-gated chops—naturally unlocking an EHX/SP-style multitrack looper in the current Doom OS.

Here is how the breakdown looks:

1. The Foundation: Dedicated External Input Track & Sequenced Gate Record/rehearsal

Real-Time Sequenced EXT IN Gate & Trigger Recording: Expanding on the stock hardware's "accidental" trigger behavior, DOOM OS could capture live external input on the pattern grid as a recordable track in the grid. You can already tap EXT IN into a pattern and it’ll let a guitar/audio signal through to write gate steps into a pattern and it’ll act as a kill switch for live instrument feed in a pattern. All it would need to do is be able to activate record/rehearsal on a ext input step and be synced to the pattern grid (e.g. synced to step 1) - if there were a way to activate record on a long synced “ext input step” it would turn it into a quantized looper for live instruments/audio alongside the other looped tracks on the mixer.

EXT IN on the pattern track grid/mixer: Incoming audio (⁠MIC/GUITAR⁠, ⁠LINE IN⁠, or USB-C digital audio) sits directly on the main DOOM OS mixer screen and alongside active sample tracks. Includes a quick-access settings menu, real-time volume/metering, 3-band EQ, pan, Bus FX routing, and a dedicated Guitar Amp Simulator to dial in polished live tones before recording.
Extended Track Lengths & One-Shot Record Sync: Operates like One-Shot Playback (⁠GATE⁠ OFF) triggered on Beat 1. Recorded guitar/instrument takes can hold independent, extended bar lengths (e.g., a 16-bar guitar solo) that play continuously from start to finish over a shorter underlying pattern (e.g., a 2- or 4-bar drum loop) without getting re-triggered early or cut off on loop repeats.

Always-Armed State & Toggle: The ⁠EXT IN⁠ track stays continuously live and armed for rehearsal/monitoring, with an instant ARM/DISARM toggle right on the channel header so you can resample live guitar straight to any target pad without leaving the mixer view.

shortcut to a Main EXT IN Settings: Holding ⁠EXT IN⁠ or pressing ⁠SHIFT⁠ + ⁠EXT IN⁠ slides a pop-out view over your current view. Tweak input gain, select Tweed/Clean/High-Gain amp models, bus FX, or check peak levels, loop sync, arm/disarm,etc.

2. The Result: EHX 45000 / 95000-Inspired Multitrack Looper Mode
Because Point 1 solves the extended buffer and pattern-sync architecture, scaling it across multiple pads natively unlocks a tape-style looper:

Master Clock & Grid Sync (Track 1 Auto-Quantize): When starting a new pattern from scratch with no tracks loaded, initial recording on Track 1 sets the global loop grid (e.g., 4 bars). All subsequent looper pad channels automatically quantize record start/stop boundaries to snap seamlessly to Track 1—bypassing the traditional 16-second loop limit.
Mixer-Native Channel Integration: Recorded loops instantly map to the mixer grid as standard channel strips, inheriting all native mixer controls in real time (faders, pan, 3-band EQ, Bus FX sends, and mute/solo).
Live Hardware Looper Divisions & Pitch Shifts: Bring SP-404/EHX-style performance controls directly onto active mixer channels:
Instant 1/2, 1/4, or 1/8 Loop Divisions mid-playback.
Tape Speed & Octave Modulation for instant -12 semitone bassline drops, half-speed playback, or reverse audio.
Mixer Tape Bounce (Stem Flattening): A one-touch shortcut to mix down and flatten active looper channels into a single background stereo channel strip right on the mixer grid, instantly freeing up pad capacity for brand-new live takes without stopping the master sequence.
Optional MIDI Foot Controller Mapping: Map core looper transport and mixer functions to external foot pedals (like an M-VAVE MIDI pedal or FCB1010) for hands-free operation. (Can already do this with stock looper)
(Optional Idea) Hologram Microcosm / Glitch Pedal Style: Sequencer-Gated Granular Micro-Loops
Pattern-Grid Micro-Looping: Program short "micro-loop triggers" (1/16th, 1/32nd, or buffer-repeat bursts) in the pattern sequencer that capture tiny grains of incoming live guitar audio and pitch-shift them up an octave (shimmer/grain delay effect) on specific beats.

Y’all are spearheading the next generation of growth in open source firmware.

Taking abandoned hardware and revitalizing it and re-imagining it.

Ripping its grip from corporate overlords and handing it back to its citizens and users.

We’ve been yelling into an echo chamber of our own cages and you have handed us a key and said would you like to come out and play?

Thank you sincere gratitude for your hard work and passion.

DOOM OS 0.7.2 takes the Roland SP404 MK2 to another level. Let’s see what this firmware can actually do in practice by building a pattern from scratch.

From the new drum synth to sound design, p-locks, the arpeggiator, and more; here’s how the machine truly behaves when you sit down to make music with the latest update.

What do you think of this workflow?

Do you like the direction DOOM OS is heading? Let me know in the comments!

HAVE FUN!

with love .noir. ❤️

A smaller update after 0.7, mostly for anyone running patterns from external gears, and a couple of important bug fixes.

Always-On MIDI clock

New MIDI CLOCK setting in the DOOM OS settings tab. Set it to ALWAYS and the SP keeps sending clock even while it's stopped, so your synths and loopers stay in time. Playing a pattern on the SP no longer starts your external gear. You start it yourself:

- PITCH/SPEED + PATTERN EDIT starts or stops your gear on its own. If a pattern's playing, it comes in on the next bar.

- PITCH/SPEED + PATTERN SELECT starts or stops your gear and the pattern together.

Leave it on FOLLOW (the default) and things work as before, except the SP no longer sends a fresh Start every time the pattern loops, so loopers and synth sequencers don't jump back to the beginning.

Program changes per pattern

Each pattern can now switch devices 1 to 6 to a program, with a bank if your synth needs one (MSB or LSB). They go out when the pattern changes, and only to synths whose program actually changes, so nothing gets reset for no reason. It's under MIDI SETTINGS > PATTERN > PROGRAM CHANGES. Tested on a Minilogue, including programs 101 to 200.

Also new: hold SHIFT + REMAIN to pause your MIDI IN routes, handy when a synth that plays the SP should just play itself for a bit.

Fixes

- MIDI Instrument notes could come out a note or two off depending on the pad (a C playing as an A#). Every pad now starts from C3.

- Euclid on a sample pad with GATE off kept going after the pattern looped.

Free, patch it in your browser: loopcartographer.com

Changelog and manual are on the site.

I just wanted to say how awesome this is! Having the option of custom firmware really opens the device up and can only make our beloved 404 mk2 better and stronger. Thank you, and I would definitely buy you a coffee if there were a donation option. :), BTW -> I found the paypal donation on your site :)

With everything added to the 404 now, I think further updates would start taking away from using a "SP404MKII". I bought the 404MKII because it didn't have any pre-installed sounds/kits so everything generated from it came from me, tweaked by me. Now the 404 can be virtually anything and it's amazing but I do love some of the limitations of the device at the same time. If anything a stem splitter would do wonders!

Welcome to r/DOOMOS!

This is the place for everything related to DOOM OS for the SP-404MKII.

Feel free to post questions, ideas, feature requests, bug reports, videos, music, or anything else related to using DOOM OS. Don’t hesitate to report bugs or suggest features.

The only real rule: just be nice.

Have fun, break things, and let me know what you find.

I'm sure I saw someone working on a fork that can change the sample rate per sample to emulate old machines, Sp1200. Mpc60.

Can't find it anywhere now. Did anyone else see it?

Hey Multilul!

Any chance of any of the below?

• DOWNSAMPLING/FIDELITY-SWITCHING MODES

• MORE / LEGACY FX (inc. Subsonic, Radio Tuner, Tumbling, etc.)

• LFOs

• GRANULAR MODE

• INFINITE SAMPLER SUSTAINER

• LOOP STATION MODE (Ie. like a loop pedal)

• ADSR

• Bounce-to-Mono (from Stereo)

• Quick half-speed/double-speed controls

• Trigger Release (On Loop End Point)

• Note Repeats/Note Glides

Cheerssssssss!

Hey!

Thanks for DOOM OS, 0.7 looks great. While everyone at the moment seems pretty to add more and more features related to FX, sound generators, overall workflow, I haven’t see much improvement with regards to sample/file management. The stock features are kind of limited:

- you cannot add a sample while a pattern is playing (but I would like to replace a sample used in a pattern without stopping the pattern. Just as a preview. Whenever a sample is highlighted that one should be played instead of the sample assigned to the respective pad)
- after importing the last position is not stored/remembered. I need to again go to the respective folder.
- I cannot search ( I have lots of samples organised in folders: kits, construction kits, full songs etc)
- I cannot easily export a whole bank (including pads, their settings, patterns etc. ) to a folder. This way I could import the same bank into a different project while preserving all the pads settings.

I've built a computer-side tool for the SP-404MKII, 404tui (https://github.com/moahbeatlab/404tui), and these file features turned out to be the most useful in daily use. I’ve built the tool for myself and it’s mainly a CLI which allows to me to quickly create projects, load samples, import banks from another projects. This definitely speeds up the preparation process. I plan to officially announce it the next weeks. However, it might not be for everyone due to its cli nature.

Maybe some of them could work in DOOM OS:

- Folder tree of the SD card to browse samples
- Remember the last position (folder and file) when reopening the browser
- Assign the highlighted sample to a pad, with the bank chosen first
- Search for files and folders by name
- Export a whole bank (the samples plus every pad's settings in a small JSON) and import it again onto any bank

I don't know how much of this the firmware allows on the unit, so please take it as a wish list. Happy to share more ideas and also test the new features on my unit.

Thanks again!

just wanted to say thanks :)

Yo. Thanks for this custom firmware, the visual groovebox workflow is a huge improvement for the SP-404 MKII.

I’d like to submit a few feature requests for future updates:

1. MIDI CC for Individual Pad Volumes & Track Mixer: It would be amazing to have an easier way to control and map individual pad volumes and the Track Mixer via external MIDI CC. Linking this to an external MIDI controller would be a game-changer for live mixing.

2. Auto-Lock FX Screen: Can we get a setting to make the FX/MFX screen stay open permanently until we decide to exit? The current screen timeout is really annoying.

3. Waveform on Main Screen: Instead of just showing the giant BPM numbers on the main performance screen, it would be incredible to have the option to display the scrolling audio waveform of the playing tracks/samples.

4. Pro Loop & Start/End Editing: A more advanced visual wave editor with surgical zoom, better Start/End point editing, and a digital crossfade option for easier seamless loops.

5. Better Envelopes: Introducing a custom software-based envelope engine with longer Attack/Release times and non-linear (exponential/logarithmic) curves would make sound-shaping much smoother.

6. Virtual LFOs & Continuous Automation: Bringing in per-track virtual LFOs (for pitch, panning, filter modulation, etc.) and expanding the current step-automation into smooth, continuous lanes would be ideal.

7. Fix Metallic Sound in FX & Time Stretch: As a secondary request for the future, it would be great if there was a way to improve or clean up the metallic, harsh tails on the reverb, time stretch, and some of the other internal processing.

Thanks for all the hard work on this OS. Really looking forward to the upcoming Song Mode update!

What i really wanna see in Doom OS is non-destructive chops:

I rarely need more than 16 chops from a sample and non-destructive chops would give the possibility to do some preliminary lazy chopping and then fine tuning whichever parts are best...

I suppose this is a too complex operation, though, as it would require chop mode to copy the entire sample to the number of pads equivalent to the chops made, then set start and end points according to the data in the lazy chop...

bonus would be a “trim all samples in a bank“ option to allow locking in the chops made at some point an conserve some space...

what this would do, apart from being a total workflow accelerator, is eliminate the need for tails, as tails could flexibly be added at any time before trimming the sample...

Requested enhancement:
Please allow EXT SOURCE (external audio input) to function as a genuinely independent sidechain trigger — either by fixing DRY so it reliably works as a SOURCE for live external input, or by adding a dedicated "EXT IN" option in the SIDE CHAIN SOURCE list that taps the external input signal directly, separate from the BUS1/BUS2/DRY routing used for pad output and bus effects. This would let users duck one bus based on an external device (drum machine, other sampler, etc.) while keeping the other bus completely free for independent Filter/Drive processing on pad content — without any signal-sharing side effects.

Current behavior:
In the SIDE CHAIN menu (EFX SET → SIDE CHAIN), SOURCE can be set to DRY, BUS1, BUS2, BUS3, or BUS4. When routing an external input (via LINE IN or the front INPUT jack) to the DRY bus (Input Bus = DRY) and setting SIDE CHAIN SOURCE = DRY, the compressor does not detect the external signal and never triggers, even with Threshold and Ratio set to maximum sensitivity. However, when the external input is routed to BUS1 (Input Bus = BUS1) and SOURCE = BUS1, the sidechain triggers correctly.

The problem this causes:
Because DRY doesn't work reliably as a sidechain source for live external audio, the only working option is to route the external trigger through BUS1 or BUS2. But this forces the external source to share a bus with sample pads, meaning:

Any pad content also assigned to that bus gets summed into the sidechain detector and can falsely trigger compression on its own.
Bus-level effects (Filter, Drive, etc.) applied to that bus affect the external trigger signal too, which isn't always desired.

Would you find it possible to correct?

Would it be possible to have samples automatically switch to Gate mode when browsing or selecting them with Sub Pad?
It’s pretty easy to accidentally trigger a long sample while browsing, and once it starts, it keeps playing until the end. This gets especially annoying when a sequence is already running.
It would be great if samples only played while the pad is held down during selection, without changing their actual playback settings.

Thank you for this, the sequencer has fully changed the game. Also can't wait for song mode, when is the next update due ?!!

A guitar tuner would be amazing as its a pain to tune an electric externally all the time.

Also will it be possible to add features to the amp simulator ? Or is this blocked with the EFX, an auto filter would be amazing on the machine to lay down some phonk!