MIDI basics

What is MIDI SysEx, and how do I back up my synth?

Most synths can save their sounds outside the instrument using MIDI System Exclusive messages, usually shortened to SysEx. It is the oldest and most widely supported way to back up patches, and it still works with current gear. Here is what is going on, and a routine that keeps your sounds safe.

What a SysEx message is

Ordinary MIDI messages are short: a note, a controller move, a program change. A SysEx message can be any length. It starts with the byte F0, then a manufacturer ID (43 is Yamaha, 42 Korg, 41 Roland, 01 Sequential), then data in a layout that manufacturer defines, and it ends with F7. Every byte in between stays below 128, which is why some instruments pack their data before sending it.

A patch dump is one or more of these messages carrying a sound, a bank of sounds or the instrument's settings. A Yamaha DX7 bank, for example, is a single 4,104-byte message holding 32 voices.

Dump requests

There are two ways to get a dump out of an instrument. You can start it from the front panel, if the instrument has that function, or send a dump request: a short SysEx message asking for a sound or a bank. Requests often include a channel or device number that must match the instrument's settings, and some instruments need a setting switched on before they answer.

There is also a universal Identity Request, F0 7E 7F 06 01 F7, which many devices answer with their manufacturer, model family and firmware version. It is a good first test that the connection works in both directions.

.syx files

A .syx file is simply the raw bytes of one or more SysEx messages with no wrapper, which is why so many librarians and editors can read it. Standard MIDI Files (.mid) can also carry SysEx alongside notes. Keep your .syx files somewhere that is itself backed up, and name them well: the file name is often the only label a bank has.

Pacing: why slow matters

A classic DIN MIDI cable runs at 31,250 bits per second, roughly 3,000 bytes a second, and older instruments need time to process each message before the next one arrives. Send a stack of messages too quickly and an instrument may drop some without showing any error.

Some manufacturers document a gap: Roland asks for at least 40 ms between packets, and Novation for at least 20 ms between messages on the Circuit. Where nothing is published, 150 ms between messages is a conservative start. A gap applies between messages, not inside one, and some USB MIDI interfaces are reported to drop long messages, so for a large bank a DIN interface can be the more dependable route.

Checksums

Many Roland and Yamaha messages end with a checksum byte calculated from the message's contents so that the covered bytes and the checksum add up to a multiple of 128. If a byte changes in transit, the sum no longer works out and the instrument may refuse the message.

A checksum detects damage; it does not repair it. Recalculating the checksum after you deliberately edit bytes is legitimate. Recalculating it to make a damaged capture look valid only hides the damage, so capture again instead.

A safe backup routine

The rule that matters most: keep a copy of what is on the instrument before you send anything to it.

  1. Connect the synth's MIDI out (or its USB port) to your computer or device and confirm the connection, for example with an Identity Request.
  2. Capture everything before you change anything: every bank, plus global settings if the instrument can send them.
  3. Check that each capture is complete and, where the format has one, that its checksum is valid.
  4. Name the files clearly and copy them to a second place.
  5. Only then send new sounds. Sending a bank usually overwrites every slot in it at once.
  6. After sending, check the sounds on the instrument itself.

Doing this with Syxloom

Syxloom covers each step on iPhone, iPad or Mac. Monitor captures dumps and marks incomplete ones; the inspector checks framing, length and supported checksums and shows patch names for the formats it recognises; .mid imports have their SysEx pulled out; pacing profiles remember a gap per instrument; and Review transfer shows exactly what will be sent before you confirm. Request presets include the Identity Request. Workspace backups (.syxworkspace) hold the whole library with its names and notes, and they are not encrypted. Syxloom handles MIDI 1.0 SysEx only.

For instrument-specific walk-throughs, see the guides for Yamaha DX7 and FM synths, Korg logue synths and Sequential Prophet synths and the DeepMind 12.

Where Syxloom fits

Syxloom is our SysEx librarian for iPhone, iPad and Mac; one purchase covers all three. Its format support is based on published MIDI specifications, and layouts that come from community documentation are labelled in the app. It has been tested on simulators, with a virtual MIDI harness on the Mac and with large generated test libraries, not with physical instruments, and it cannot confirm that an instrument received or stored a patch.

Syxloom is also sold with Midiary, our Standard MIDI File studio for iPhone and iPad, in the MIDI Toolkit bundle on the App Store.

The app in this guide

Every app here is one we make. This guide is checked against the live catalogue each time it changes — if an app named here ever left the store, the build would drop it rather than link to nothing.

Yamaha, Korg, Roland, Sequential and Novation are trademarks of their respective owners. They are named only to describe compatibility; Shadowfetch is not affiliated with or endorsed by them.

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