Thanks MIDI2XS. I was aware of the device ID used with Sysex but was referring to this:
Universal system exclusive messages
There are two universal IDs that can be used by system exclusive messages instead of the specific manufacturer IDs above. Since these two IDs are not specific to a manufacturer, but universal, all MIDI devices should consider responding to those. These IDs are as follows.
Hexadecimal value Decimal value Description
0x7E 126 Real time
0x7F 127 Non-real time
In other words, 0x7F is carried by system exclusive messages to which all MIDI devices should respond to in real time (immediately) and 0x7E is carried by system exclusive messages to which all MIDI devices will respond to, but not in real time (not necessarily immediately). For example, the MIDI full frame message is a system exclusive message with manufacturer ID 0x7F. This message prompts all MIDI devices to immediately cue up to a certain point in time.
The first byte after the real time / non-real time ID is the "system exclusive channel". Normal system exclusive messages do not have a channel, but universal system exclusive messages do have a channel that could be from 0x00 to 0x7F (from 0 to 127). Normally, the system exclusive channel will actually be the manufacturer ID in the table above (e.g., 0x41 for Roland), so that the message can be sent to a specific MIDI device. If the system exclusive channel is 0x7F then this message is for all MIDI devices.
The two bytes after the system exclusive channel are sub-IDs and describe what the message is about. For example, the two bytes '0x01 0x01' show that the message is the MIDI Full Frame message and that the rest of the data should be used to discern time to which the MIDI device should cue.