PlantHolder
Firmware for Workshop System Computer (Music Thing Modular)
USB MIDI host and Placeholder-style reverb — built for the Instruo Pocket Scion, happy with any USB MIDI device.
by Phil Miller
- Distribution
- Prebuilt image you flash yourself
- Source
- github.com https://github.com/TomWhitwell/Workshop_Computer/tree/main/releases/85_plant_holder
- Homepage
- computer.musicthing.co.uk https://computer.musicthing.co.uk/programs/85-plant-holder/
- Synced from
- upstream metadata, raw.githubusercontent.com https://raw.githubusercontent.com/TomWhitwell/Workshop_Computer/main/releases/85_plant_holder/info.yaml. Corrections belong upstream.
- effect
- reverb
- midi-host
- midi-to-cv
- cards
Description
Originally a companion for the [Instruo Pocket Scion](https://instruomodular.com/product/pocket-scion/), now a generally fun stereo reverb that's also a **USB MIDI host**. Plug in the Scion or any USB MIDI device — the Computer will power it — and break MIDI channels **1** and **2** out as v/Oct + gate (route voices in the Scion companion app, or your device's MIDI Settings).
The reverb is modelled on the Fairfield Circuitry **Placeholder (EB)** — three cross-coupled delay lines with a tone-tilted feedback path. **DECAY self-oscillates around 2–3 o'clock**, highly interactive with Size, Tone, LPF, and Mix.
The name nods to the Scion's plant-biosonification heritage and to the Householder reflection matrix at the heart of the Placeholder's feedback delay network.
Requires a **Rev1_1** board (Q2 2025 or later) for USB host mode.
Install notes
Copy the UF2 onto the Computer's program card (RP2040 bootloader drive).
Version history
| Version | Date | Notes |
|---|---|---|
| 0.2.0 | 2026-08-06 | Version and date from the card's info.yaml. |