Puck MIDI Note On

A Guess that you can try to see if it works.

I don't have a Puck and not an expert but some poking around the web provides a guess.

You might try:

midi.send(0x9, 60, 100)

A Note Off can be implemented by sending a Note ON with a velocity of 0.

The Puck.js+MIDI page

Puck.js+MIDI

The send function as found in

ble_midi.js

exports.send = function(channel, controller, value) {
  NRF.updateServices({
    "03B80E5A-EDE8-4B33-A751-6CE34EC4C700": { // MIDI
      "7772E5DB-3868-4112-A1A9-F2669D106BF3": {
        value: [0x80, 0x80, 0xB0 + channel, controller, value],
        notify: true
      }
    }
  });

The send command sends a 4 byte long MIDI message. The content of the 4 bytes determines the meaning of the 4 byte message and is defined in :

From Section 4 of MIDI10.pdf

MIDI10.pdf

From Table 4.1 a Note On uses channel 0x9 and a Note Off uses channel 0x8.

You might try:

midi.send(0x9, 60, 100)

A Note Off can be implemented by sending a Note ON with a velocity of 0.