MP3 to MIDI System Real-Time Messages: Eight Bytes, Six Meanings, No Slot in the File
The F8 to FF block is the only family in the protocol whose members are all one byte with no data bytes at all. Eight status bytes, six of them carrying a meaning, and no event type in a MIDI file for any of them.
Short answer
- Eight rows, no data bytes. Every code in the F8 to FF block is exactly one byte: the data-byte column is empty on all eight rows.
- Six meanings, two blanks. F9 and FD are Undefined; the other six are a clock, three transport commands, a keep-alive and a reset.
- None of them reached the file. The grammar admits three event kinds and only channel messages count as a MIDI event, so the block has no event type of its own.
- Nothing to lock to afterwards. A converted file carries timing as delta-times and a tempo map, not as a rate arriving on a wire.
Eight rows, no data bytes
The message table splits into five blocks, and the real-time block is the odd one out. Elsewhere the column is populated: channel messages carry one or two data bytes, and three of the system common rows are followed by data. In the real-time block the data-byte column is empty on all eight rows, so nothing in it can be addressed or carry a value. Two rows are Undefined, F9 and FD, and the six that remain never name a note or a channel.
The clock byte has no number in it
Timing Clock is defined as sent 24 times per quarter note when synchronisation is required. It carries no position and no count, so all of its meaning is in its arrival rate. When a file names no tempo the format supplies 4/4 and 120 beats per minute, where 24 clocks per quarter note is 48 messages a second, one every 20.8 milliseconds.
The only message that acts by not arriving
Active Sensing is the single code whose defined effect is triggered by its absence. The specification calls its use optional: after the first one the receiver expects another within 300 milliseconds at most, or it assumes the connection has been terminated, turns off all voices and returns to non-active-sensing operation. The failure mode is silence rather than stuck notes. That window is 14.4 clock periods, or 0.6 of a quarter note.
The transport commands are not symmetrical. Start is annotated as the message that will be followed with Timing Clocks; Continue resumes at the point the sequence was stopped, so Stop parks the position and only Reset discards it.
A file has an event type for none of it
The file grammar admits three kinds of event, and a MIDI event is any MIDI channel message, so the real-time block falls outside the grammar rather than into a category of its own. It is named once, in the description of the escape, as one of the things that would not otherwise be legal in a file.
General MIDI asks for four things, none about time
The level 1 minimum requirements are four items: 24 voices at once, respond to note velocity, all 16 channels with channel 10 reserved for percussion, and polyphony on each channel. The word clock does not appear, so a device can meet every stated minimum while ignoring all six codes.
What it means for a converted file
Nothing was lost in the conversion: none of it was ever part of a file. Timing in a file is numbers attached to each event: a delta-time measured against the division in the header, plus a tempo map saying how long a tick lasts. Nothing in it can time out: the 300 millisecond rule describes a connection, not a file.