SysEx

SysEx — System Exclusive — is the escape hatch in MIDI, the place anything not covered by the standard goes: patch dumps, firmware uploads, secret parameters, vendor-specific everything. Universal Controller MIDI lets you fire arbitrary SysEx blobs from any button, trigger, or stick.

If your synth has a feature the front panel can't reach, there's almost certainly a SysEx command for it.

The framing

Every SysEx message is bracketed by F0 (status start) and F7 (status end). Between them: a manufacturer ID (1 or 3 bytes), a device ID, and the payload. Every payload byte must be 7-bit — 0x00 to 0x7F. Anything 0x80 or higher is reserved for status bytes and will corrupt the stream.

# Korg Volca Sample — set part 1 sample number to 12
F0 42 30 00 01 2D 0C 00 F7
#   ^^ ^^ ^^ ^^^^ ^^ ^^ ^^
#   |  |  |  model |  |  end
#   |  |  device   |  param value
#   Korg ID        Korg fn

Authoring SysEx in the mapping editor

In the mapping editor, set the output type to SysEx and paste a hex string. Spaces are optional. The F0/F7 framing is added for you if missing — but never wrong to include it. For dynamic payloads, use {value} to inject the current input value as a 7-bit byte; e.g. F0 41 10 42 12 40 00 04 {value} F7 for a Roland JV-style filter cutoff.

{
  "input": "RT",
  "output": {
    "type": "sysex",
    "bytes": "F0 41 10 42 12 40 00 04 {value} F7",
    "value_range": [0, 127],
    "value_curve": "linear"
  }
}

Common manufacturer IDs

The 1-byte IDs are the originals; 3-byte IDs (prefixed with 00) were added when the namespace ran out. Reference table for the ones you'll hit most often:

Real-time vs bulk

Realtime SysEx (parameter change) is short, fast, fine on a per-input basis — fire it from a button or stick all day. Bulk SysEx (patch dumps, firmware) is long, can be 10 KB+, and shouldn't be tied to a held input. Trigger bulk transfers from a single button press, not a continuous source.

Real-world scenarios

SysEx earns its place when you need to do something the synth pretends isn't possible:

1. Prophet 6 voice-mode toggle. Map Triangle to send F0 01 2D 06 12 ... F7 — instant flip between poly / mono / unison without diving into the menu mid-track.
2. Roland MC-707 scene recall. D-pad sends scene-change SysEx (Roland scene-change CC isn't enough for full state). Four scenes on one cross-pad.
3. Elektron Digitakt pattern jump. Face buttons fire the pattern-change SysEx with sample-accurate quantisation that the standard Program Change can't guarantee.
4. NI Maschine Jam-style page flip. Touchpad swipe sends Maschine's group/page SysEx so you control hardware Maschine from a DualSense as if it were a Jam.
5. DX7 patch initialise. Hold Share + L3 to push a fresh init patch — perfect when you've FM-ed yourself into a corner during sound design.

SysEx is a Pro feature. Free maps notes and CCs only.