Why Does MIDI Offer 127 Notes

Question

Is the 127 note values in MIDI musically significant (certain number of octaves or something)? or was it set at 127 due to the binary file format, IE for the purposes of computi

Answer 1

Simple efficiency.

As a serial protocol MIDI was designed around simple serial chips of the time which would take 8 data bits in and transmit them as a stream out of one separate serial data pin at a proscribed rate. In the MIDI world this was 31,250 Hz. It added stop and start bits so all data could travel over one wire. It was designed to be cheap and simple and the simplicity was extended into the data format.

The most significant bit of the 8 data bits was used to signal if the data byte was a command or data. So- To send Middle C note ON on channel 1 at a velocity of 56 A command bytes is sent first and the command for Note on was the upper 4 bits of that command bit 1001. Notice the 1 in the Most significant bit, this was followed by the channel ID for channel 1 0000 ( computers preferring to start counting from 0)

10010000 or 128 + 16 = 144

This was followed by the actual Note data

72 for Middle C or 01001000

and then the velocity data again specified in the range 0 -127 with a 0 MSB

56 in our case

00111000 So what would go down the wire (ignoring stop start & sync bits was)

144, 72, 56

For the almost brain dead microcomputers of the time in electronic keyboards the ability to separate command from data by simply looking at the first bit was a godsend.

As has been stated 127 bits covers pretty much any western keyboard you care to mention. So made perfectly logical sense and the protocols survival long after many serial protocols have disappeared into obscurity is a great compliment to http://en.wikipedia.org/wiki/Dave_Smith_(engineer) Dave Smith of Sequential Circuits who started the discussions with other manufacturers to set all this in place.

Modern music and composition would be considerably different without him and them.

Enjoy!