How to send NRPN messages with pygame midi

Question

I'm writing a program that will read incoming cc messages from a device that can only send cc's and send it to another device as an nrpn message. I know how to send cc messages from pygame but I can't wrap my mind around how to send nrpn's. I looked at the Vriareon code and I don't see anywhere in there were it even accesses midi. Can anyone give an example of how this is done?

Thank you!

Answer 1

NRPN messages are CC messages.

However, NRPN numbers are distinct from CC numbers. The MIDI specification says:

Controller number 6 (Data Entry), in conjunction with Controller numbers 96 (Data Increment), 97 (Data Decrement), 98 (Non-Registered Parameter Number LSB), 99 (Non-Registered Parameter Number MSB), 100 (Registered Parameter Number LSB), and 101 (Registered Parameter Number MSB), extend the number of controllers available via MIDI. Parameter data is transferred by first selecting the parameter number to be edited using controllers 98 and 99 or 100 and 101, and then adjusting the data value for that parameter using controller number 6, 96, or 97.

To change a controller like volume (7), you would send a single message:

B0 07 xx

To change an NRPN, you would select the NRPN first:

B0 63 mm
B0 62 ll

And then change the currently selected NRPN with the data entry controller:

B0 06 mm
B0 26 ll  (optional, for 14-bit values)

So setting NRPN 0:1 to value 42 could be done with:

self.midi_out.write_short(0xb0, 0x63, 0)
self.midi_out.write_short(0xb0, 0x62, 1)
self.midi_out.write_short(0xb0, 0x06, 42)