DOOM OS: Custom Firmware for the Roland SP-404MK2

DOOM OS is a custom OS for the Roland SP-404MK2 featuring a graphical step sequencer, mixer with 3-band EQ per track, instruments & kits, live waveform visualizations, intuitive sidechain editor, and much, much more!

Version 0.7.4, build 651C, for firmware 5.52.

Open the patcher Quickstart manual GitHub Reddit Patreon Discord

Features

A closer look

Pattern grid Edit your patterns on a graphical step sequencer. Add or remove notes directly on the grid, and adjust individual steps using the CTRL knobs.

Zoom view Zoom in to see four tracks across two bars, with notes displayed at their actual lengths. Switch to the piano roll to edit individual pitches.

Mixer Mix your tracks with individual volume faders, pan controls, effect bus routing and real-time level meters.

3-band EQ Give any pad its own 3-band EQ from the mixer, with its curve drawn over the channel strips. Set LOW, MID and HIGH with the CTRL knobs, or open ADV to set the frequency and Q of each band.

Side chain Visually configure sidechain ducking with an interactive bus diagram. Choose the source and destination buses, adjust the parameters, and see the ducking in real time as your pattern plays.

Bounce in place Resample a track with its effects to the next available pad and automatically replace the original track with the result. Use Undo to restore the original track.

Track panel Access track controls such as mute, solo, volume and track management. Swap tracks between pads or delete tracks directly from the panel.

Recording Record notes directly into your patterns using the pads. Set quantization, swing, velocity and note length for new recordings.

Effect automation Record effect parameter changes in real time using the CTRL knobs. View and edit automation for individual effects and steps in the automation editor.

Pattern tools Quantize, add swing, shift, double, halve, reverse, humanize or transpose your patterns. Apply changes to individual tracks or entire patterns, with up to 12 levels of undo.

Instruments and kits Add instruments and drum kits to your tracks, and customize their sound using the Instrument Editor.

Instrument editor and parameter locking Adjust instrument parameters with live graphs for envelopes and other settings. Every parameter can also be locked to individual steps.

Real-time mixer waveform Monitor the main output or individual tracks with a live waveform displayed directly over the mixer.

Real-time pattern grid waveform Display a live waveform over the pattern grid, showing the main output or an individual track while you edit your pattern.

Arpeggiator Create arpeggios with support for musical scales and a variety of patterns. Render the generated notes directly to a track for further editing.

Help mode Hold SHIFT for three seconds to activate context-sensitive help. Press any button or turn a knob to see what it does, without triggering any actions.

Custom shortcuts Create up to eight custom button combinations to access your favorite DOOM OS or stock firmware screens.

Boot animations Choose from different boot animations, or select RANDOM for a different animation each time you start your SP-404MKII.

How to install

Firmware 5.52

1. Get the firmware from Roland

Download the system update from Roland's support page and unzip it. You need the SP404MKII_APP1.bin file inside; the other file, SP404MKII_APP0.bin, is not needed.

2. Load the file and patch it

You can find the patcher here.

3. Install it on the SP-404MK2

Back up your data first.
Copy the patched SP404MKII_APP1.bin to the root of the SD card.
Put the card in the SP, hold SHIFT and switch it on. Wait for the updater menu and press the VALUE knob.
When the update is done, switch the SP off and on again.

First steps

Every control

It’s recommended to read the full manual, as there are too many new features and shortcuts to cover here.

REMAIN+SUB PAD: Open DOOM OS! (works from any screen)
EXIT: Close DOOM OS and save your changes
SHIFTheld 3 s: Help mode: press any control to see what it does
PATTERN SELECT: Start / stop
Pads 1-16: Turn steps on or off in the selected row
VALUEturn: Select a row
SUB PADheld+tap pads: Choose the sample for a new row
a held step+CTRL 1-3: Velocity / length / timing of that step
a held step+SHIFT+CTRL 1: Pitch of that step
VALUEpress: Open the piano roll
HOLD: Play the pads instead of editing steps
REC: Press once to rehearse, again to record
PATTERN EDIT: Pattern tools
RECORD SETTING: Show track panel or pattern panel
RECORD SETTINGheld: Open the mixer
START/END: Open the instrument editor on an instrument track
SHIFT+START/END: Show live waveform view
SHIFT+PATTERN SELECT: Undo
REMAIN+PATTERN SELECT: Redo

For more information, see the manual.

Release notes

Changelog

0.7.4, build 651C (2026-11-13)

From the lab

DOOM OS: a custom OS for the Roland SP-404MK2
A heavily modified custom OS with a new graphical pattern sequencer, mixer, and much, much more!

27 September 2026

Support

DOOM OS is free and stays free. It is built in the evenings, one SP-404MK2 and a lot of coffee. If it’s useful to you, you can support its development.

Patreon PayPal Buy me a coffee!

DOOM OS is unofficial firmware. Not affiliated with, endorsed by or supported by Roland Corporation. SP-404MK2 is a trademark of Roland Corporation. Use it at your own risk. DOOM OS is named in homage to MF DOOM.