SysEx data stream format
A midi SysEx data stream has a special format, since midi data above hex 7F
is illegal (interpreted as control codes). After the SysEx header, i.e. starting
with byte number 6, the data stream can be divided in sequences of 8 bytes.
The first byte in a sequence is always the "bit bucket", which holds
the most significant bits for each of the other 7 data bytes in a sequence. The
most significant bit of the "bit bucket" itself, is 0.
When converting TO a SysEx data stream, 7 bytes of 8-bit data is converted to
a 7-bit "bit bucket" + 7 bytes of 7-bit data.
When converting FROM a SysEx data stream, bit bucket + 7 bytes of 7-bit data
is converted to 7 bytes of 8-bit data, i.e. the above process reversed.
See Note 2 on page 220 and table 1-5 on page 215 in the N264/N364 Reference Guide.