Cathedral of the Hollow Saint
A haunted hurdy-gurdy for the original Teenage Engineering OP-1: a kennel synth plugin (hollowsaint) for the Hundekraft OP-1 Workshop 3.0.x.
- Add-on
- Beta
- Medium brick risk
This project hasn't been claimed by its maintainer yet, so its details come from the community. Is it yours? Claim it
Hollow Saint 0.7.0: Lo-Fi Relic and Crank & Tremor
A haunted hurdy-gurdy for the original OP-1: a synth engine plugin for the Hundekraft OP-1 Workshop 3.0.x. Bowed melody strings, a drone that can hold a key like real bourdons, a buzzing bridge that kicks in on wheel strokes locked to the OP-1's tempo, and a cathedral that darkens, rings and tolls a distant bell. Pure synthesis, no samples.
Pre-release: 0.7.0 has been tested in a PC build and in a Blackfin (OP-1 processor) simulator, and is now being tested on real OP-1 hardware. Please report anything odd in Issues.
What's new in 0.7.0
- Lo-Fi Relic (push green). The sound goes through a worn old tape before it reaches the cathedral: wow and flutter, warm saturation, a lower sample rate and fewer bits, dust, a darker tape head, a little hiss and a sagging transport. While it's on, turning green sets how old the tape is. It stays about as loud as the clean sound, and switching it on or off fades over ~35 ms, so it doesn't click.
- Crank & Tremor (white). The wheel strokes now also pulse the level and the string's tone. WHEEL BUZZ low gives slow, breathing swells, the middle gives a steady mechanical tremolo, and high gives an aggressive rattle with a deep pulse.
- Two new stroke rates: steady, 1 bar, 1/2, 1/4, 1/8, 1/8 triplet, 1/16.
- Screen: a worn cassette with turning reels and an age meter appears while the relic is on, with dust in the cathedral. There are icons for all 7 rates.
- Presets updated: midnight vigil breathes once a bar, crypt drone and drowned bell swell every half bar, and each preset has its own relic age.
- Faster (from 0.6.1): about 38 % fewer processor cycles than 0.6.0, with exactly the same sound. With the relic off and the wheel on steady, 0.7.0 sounds bit-for-bit the same as 0.6.1.
The encoders
| Knob | Turn | Push |
|---|---|---|
| 🔵 Blue: DRONE | off, subtle and dark, rich and resonant, dense with a sub-octave | the drone's key: FOLLOW (your lowest note) or a fixed key C to B |
| 🟢 Green: STRINGS | soft hollow flute, nasal hurdy-gurdy, bright and cutting | Lo-Fi Relic on/off; while on, green sets the tape's age |
| ⚪ White: WHEEL BUZZ | smooth, breathing swells, mechanical tremolo with buzz, aggressive rattle | the stroke rate, synced to the OP-1's tempo |
| 🔴 Red: CATHEDRAL | dry and close, hollow and old-world, a dark huge space with a distant bell | none |
Install
- Your OP-1 needs the Hundekraft firmware 3.0.x.
- In the Workshop, open Your plugins, add
hollow_saint.knl, connect by USB, click Update OP-1, then press T1 on the OP-1 to confirm. - On the OP-1, press synth, then Shift + T1, and pick hollow saint.
- Presets: unzip
hollow_saint-0.7.0-presets.zip. On the OP-1, press Shift + COM, then T3 (disk mode). Copy thehollow saintfolder fromsynthinto the OP-1'ssynthfolder, then eject.
If the OP-1 won't start after you add the plugin, power-cycle it. It boots once without plugins, and you can then remove the plugin in the Workshop.
Files
hollow_saint.knl: the plugin (40,548 bytes)hollow_saint-0.7.0-presets.zip: the 8 presets (hollow saint, midnight vigil, howling dog, ash procession, bone flute, crypt drone, plague dance, drowned bell)hollow_saint_0.7.0_demo.mp4: a 4-minute demo of the engine, the new features and the presets. It was rendered on a PC from the plugin's own sound and screen code, not recorded on an OP-1.SHA256SUMS.txt: checksums
Licence: GPL-3.0-or-later, with the OP-1 firmware permission (see LICENSE and NOTICE).
Before you start
- How hard is it?
- EasyCopy a file or use a web page. No extra software.
- What you need
- A USB or MIDI cable
- Comfort with the command line
- A computer
- Can it break my device?
- Small chance of trouble, with a way to recover.
- Can I undo it?
- The project doesn't say. Assume you can't.
Did it work for you?
Did Cathedral of the Hollow Saint v0.7.0 work on your Teenage Engineering OP-1?
No reports yet for v0.7.0.
One-tap reports from owners. Bricked reports are checked before they count.
Compatibility
Devices: Teenage Engineering OP-1.
No compatibility information yet.
Getting started
From the project's README ("Install"):
- The OP-1 must run Hundekraft 3.0.x (the kennel core). First installation is a full firmware build from the Workshop through the boot menu; see the Workshop's quick start.
- In the Workshop, open Your plugins, add release/hollowsaint.knl, connect the OP-1 by USB and press Update OP-1. Review, send, then press T1 on the OP-1 to confirm. It installs on the confirmed restart (no hot reload).
- On the OP-1: synth, then Shift + T1, choose hollow saint.
- Presets: Shift + COM, then T3 (disk mode). Copy the folder release/presets/synth/hollow saint into the OP-1's synth folder and eject.
If the OP-1 does not start after adding a plugin: power-cycle it; it starts once without plugin files, then remove the plugin in the Workshop.
Risk and recovery
- Brick risk
- Medium
- Requires opening the device
- No
From the project's README ("Install"):
- The OP-1 must run Hundekraft 3.0.x (the kennel core). First installation is a full firmware build from the Workshop through the boot menu; see the Workshop's quick start.
- In the Workshop, open Your plugins, add release/hollowsaint.knl, connect the OP-1 by USB and press Update OP-1. Review, send, then press T1 on the OP-1 to confirm. It installs on the confirmed restart (no hot reload).
- On the OP-1: synth, then Shift + T1, choose hollow saint.
- Presets: Shift + COM, then T3 (disk mode). Copy the folder release/presets/synth/hollow saint into the OP-1's synth folder and eject.
If the OP-1 does not start after adding a plugin: power-cycle it; it starts once without plugin files, then remove the plugin in the Workshop.
Releases
| Version | Name | Released |
|---|---|---|
| v0.7.0 | —Latest | 28 October 2026 |
Credits, license and support
- License
- GPL-3.0