SynthHub

SynthHub holds the catalogue of MIDI devices, their sounds and their firmwares, and serves it to osc-bridge and to AI apps; it grows with every use and every share. It grew out of osc-bridge on 23 October 2026, when the online server and the relay to the hardware left the public repository. Its main limit: samplers (MPC, SP-404…) are not supported yet, and a device’s sounds can only be shared if we know how to split its banks.

With no hardware and nothing to install, the site’s virtual synth lets you try it.

An engine, a format, a catalogue

Three projects fit together. osc-bridge is the free engine that talks to the devices. Open Synth Descriptors (OSD) is the open format in which the devices, their sounds and their firmwares are described. SynthHub is the service that holds the catalogue in that format: every driver in the catalogue is a valid OSD descriptor, checked by tests.

The catalogue has three readers: musicians through the site, agents through the MCP server, osc-bridge and other programs through a JSON API. The number of devices, makers and sounds changes every day; the site shows the current figures.

Getting started

On the site. The catalogue shows the devices, their shared sounds, credited to their author, and alternative firmwares.

With your hardware. The connect page lists the devices plugged into the browser (Web MIDI) and helps identify the ones it does not recognise. It then opens a relay to an AI app, which can only play recognised devices. Nothing is recorded about a device marked “private”.

With an agent. Add the server to your AI app as a remote MCP connector (in Claude: Settings, Connectors, “Add custom connector”):

https://mcp.synthhub.roomi-fields.com/mcp

There is no sign-up: the server issues an anonymous id, and a personal address (/u/<id>/mcp) keeps it from one session to the next. Then ask, for instance, which controls the minilogue exposes; the agent searches with list_devices, reads the addresses with list_routes and the documentation with get_device_docs.

Without an agent, the API can be read directly:

curl -s https://synthhub.roomi-fields.com/api/v1/index.json \
  | jq '.devices[] | select(.vendor == "Moog") | .name'

What an agent does there

• Find a driver. The agent looks the device up in the catalogue and reads its addresses and documentation.
• Play the user’s hardware. Through the connect page’s relay, it sends its messages to the recognised devices.
• Ask for approval. Every SysEx message that could change the device waits for the person to accept it on the connect page.
• Share. The agent shares sounds, with their author and licence, and reports what works on the device and what does not. Trust in a driver comes from this real use.
• Take and load a sound. Taking a sound from the machine goes through the adaptations of KnobKraft Orm, run unmodified.

What is open

osc-bridge is published under AGPL-3.0-or-later. The OSD format is dedicated to the public domain (CC0), and its schemas are served under /osd/. The catalogue data is under CC BY-SA, attributed by source. The SynthHub server’s code stays private.

Common issues

The connect page finds nothing in Safari. It relies on Web MIDI, which Safari does not offer; it works in Chrome, Edge, Opera and Firefox.

A device is not recognised on the first try. A device that does not identify itself is recognised by its port name, the messages from its knobs and users’ confirmations; turning a few knobs and confirming the model teaches the next detection.

The server address opened in a browser returns 404. That is expected: it waits for requests from an MCP app, not for a visit.

The agent can no longer drive the device. Closing the connect page’s tab ends the relay; reopen it and pair again.

A command does not do what you expect. The driver may come from documentation and be wrong: reporting it through the agent, with the device’s firmware, fixes the catalogue for the next users.

Where it stands

The service is online. What does not work yet: samplers, sound sharing for devices whose banks we cannot split, and reliable first-try recognition of a device that does not identify itself.

Site · API for agents · osc-bridge · open-synth-descriptors · the article on osc-bridge

Thanks to Christof Ruch and the contributors of KnobKraft Orm, whose adaptations are used to take and load sounds; to pencilresearch/midi (MIDI Guide) and the Electra One community preset library, the sources of a large part of the catalogue; and to everyone who shares a sound.