System Exclusive
System Exclusive carries manufacturer settings in 7-bit data, closed by a checksum.
Related
Some settings belong to no channel and require a conversation with the whole device. Those are System Exclusive messages.
The problem
A GM reset, a reverb type or a sample upload is not about one note. CC cannot do it, Program Change cannot do it, so SysEx takes over.
Protocol or message
The message starts with 0xF0 and ends with 0xF7, with a manufacturer ID and 7-bit data in between. The ID is one byte, or 00 plus two bytes. A receiver may ignore the message. Checksums are defined by the maker. GM System On is F0 7E 7F 09 01 F7. The Roland GS reset is F0 41 10 42 12 40 00 7F 00 41 F7, where the final 41 is a checksum. In a file, SysEx is stored as an F0 event with a length.
Settings and practice
Send it once before playback, not before every note. Confirm the device ID. Check after export that SysEx was not stripped. Checksum rules differ between devices, so never copy one blindly.
What to listen for
After a reset, reverb and timbre return to defaults, so the next piano sounds drier or wetter depending on what came before.
Common misunderstandings
SysEx is not audio. Not every device answers. A checksum is not encryption.
Listen in the library
All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).
Sources
- MIDI 1.0 规范对系统专用消息的结构定义，依 MMA 公开规范核查，未抄文本
- GM System On 与 Roland GS 复位的字节序列，由本地文件解析核对，未抄文本
Used for fact-checking only; all prose is original.