Opus 2.0 beta (build 1)

Opus 2 is a firmware mod for the original Teenage Engineering OP-1 on firmware #246 (not the OP-1 field). Its
small core loads plugins: .opmod files you copy into a mods folder on the OP-1's USB disk. Every feature is a
plugin, so you pick the mods and swap them as files, with no reflashing.

This is a beta. It has run in an emulator with the OP-1's own firmware and on my own OP-1, but not yet on many
others. Back up your tape, synth and drum folders first.

Get it

1. The core. Make the update on https://opus-op1.pages.dev/opus2/patcher/ from your own copy of TE's
   op1_246.op1. It runs in your browser and nothing is uploaded. Install it through the OP-1's update mode: switch
   it off, hold COM while switching it on, press 1, copy the file onto the "OP-1" disk and eject it. Never choose 7
   or 8 there, they erase your sounds and tape.
2. The plugins. Download opus2-starter-pack.zip below, put the OP-1 in disk mode (shift + COM, then T3) and drag the
   zip's mods folder onto the disk. Or take only the .opmod files you want. Then eject the disk on your computer (the OP-1 leaves disk mode): they load at the next start.
3. Coming from op1r or Hundekraft? Add bridge.opmod too (below).

Target	the original OP-1, firmware #246 only
The update	op1_246_opus2.op1, 13,144,971 bytes
Its SHA-256	42d63d5d07319f0dcf7795b493c20dc3e57c41463b680cf3a22a1ca11b04f26e
Made from	TE's op1_246.op1, SHA-256 c5315218f825f143b415ca554516541898abee843d3a236df0b54c04e1fb13a9
The starter pack	opus2-starter-pack.zip, 20 plugins, SHA-256 9dfdca508784a07875857c850d57ce21dd4d46843b70fee230750e0845aa6b63

Every file's SHA-256 is in SHA256SUMS.txt.

What's in it

• Plugins. Opus's menu (hold synth + drum + tape + mixer) lists them on T2, each with its version, memory and
  CPU, settings, controls and details. A plugin that crashes the OP-1 is left out at the next start. One that uses
  far more CPU than it should is switched off. Hold Stop while switching on to start without any.
• The starter pack: all of Opus 1's features as plugins (dimension and amp, bitcrush, chorus and plate, Fx
  overdrive's second effects, pitch bend, scales and chords, dice, zoom, tape undo and redo, play as pause, preset
  rename, overwrite save, the start-up picture), and new ones:
  • dx, a DX7 voice player with its own voices and your .syx banks from the disk;
  • outatime, a time-travel synth engine whose page is a time machine at 88 mph, its overdrive in four types;
  • iter, the OP-1's own hidden synth engine, back in the engine list;
  • Halloween, a colour theme, and the first plugin with no code at all.
• The core's own features: FN (the help key, for plugins' extra controls), voices (polyphony and unison, 1 to 6
  each), date and time, and diagnostics (menu, T3): a task manager with each plugin's and each of the OS's
  threads' CPU and memory, the audio's load over the last minute, the memory map and the battery.
• Fixed in the stock OS: the USB disk freezing Windows Explorer after a reset (USB MIDI too), recording marking
  good flash blocks as bad (credit to op1r, whose release notes also pointed at it), a save cut off by a crash, Stop
  or the power switch, running out of memory in long sessions, a large shape on the screen stopping the OP-1, and
  keys pressed during a long disk-mode start stopping it.
• The loop jump on shift + arrow is back as on stock (#1).
• Opus 1's sounds play under Opus 2 with the starter pack in the mods folder. A sound whose plugin is missing is
  kept and shows "needs" with the plugin's name.

Every plugin with its keys, CPU and memory: https://opus-op1.pages.dev/opus2/

The bridge (alpha)

bridge.opmod (opus.bridge 0.7.0) is a download of its own, not part of the starter pack. It runs op1r's synth
engines and effects (.op1p) and Hundekraft's (.knl) on Opus as they are, with their own screens and pages, and
sounds saved with them play. Put new plugin files in the disk's mods/bridge folder. The bridge's settings list
every file it found, what loaded and why a file didn't.

It's an unstable alpha, expect bugs. Opus's own plugins run much better on Opus 2, since they're made for its
core, while a bridged plugin runs through a layer that stands in for its own firmware. Not bridged: sequencers,
arpeggiators, LFOs and other features, drum and sampler engines, and engines that play samples.

op1r is by popcorp and Hundekraft's firmware by Hundekraft. Every bridged plugin stays its author's work.

Going back

te-boot, the OP-1's own updater and recovery, is never touched, so the way back is always there.

• To stock or another firmware: Opus's menu, T1 (system), the cleaner: turn green to "at restart", then
  switch the OP-1 off and on. Then install the other firmware through update mode as above (stock is TE's
  op1_246.op1). The cleaner keeps a copy of everything it changes, so installing Opus again brings it all back.
• To Opus 1: no cleaner needed, just install it.
• If the OP-1 stops at a black screen with white text: your data is fine. Hold COM while switching on and install
  Opus or your old firmware again. If a plugin is the cause, hold Stop while switching on and delete it from the
  mods folder.

Make your own

The plugin kit is in this repo, in plugin-kit/: guides,
the API reference, the SDK headers, the build tool, four example plugins (bitcrush, zoom, halloween and outatime)
and instructions an AI agent can follow, all GPL-3.0. Plugin ideas are welcome in
Discussions.

Licence

The plugins are © LizardMan, free to use and share. Their source is not published yet, apart from the plugin kit's
four examples (GPL-3.0). dx contains code derived from Google's Music Synthesizer for Android (Apache License 2.0):
its LICENSE and NOTICE are in the zip's licenses/opus.dx/ folder. The core's update file and the patcher's data
are all rights reserved: please don't share them, link to the site instead.

Opus is an independent project and is not affiliated with, endorsed by or supported by Teenage Engineering. OP-1 is
a trademark of Teenage Engineering AB. Modifying firmware is at your own risk.

Found a bug? Report it here, with your build
(hold help on Opus's menu) and the plugins in your mods folder.