Send an OSC message when a MIDI Note On message is received using python-rtmidi and pyliblo.

noteon2osc.py

#!/usr/bin/env python
#
# noteon2osc.py
#
"""Send an OSC message when a MIDI Note On message is received."""

import time
import liblo
from rtmidi.midiconstants import NOTE_ON
from rtmidi.midiutil import open_midiinput


def midiin_callback(event, data=None):
    message, deltatime = event

    if message[0] & 0xF0 == NOTE_ON:
        status, note, velocity = message
        channel = (status & 0xF) + 1
        liblo.send(
            ('localhost', 9001),
            '/midi/%i/noteon' % channel,
            note,
            velocity)

try:
    # Prompts user for MIDI input port, defaulting to ALSA on Linux
    with open_midiinput(client_name='noteon2osc')[0] as midiin:
        midiin.set_callback(midiin_callback)

        while True:
            time.sleep(1)
except (EOFError, KeyboardInterrupt):
    print("Bye.")

Latest version: https://github.com/SpotlightKid/python-rtmidi/blob/master/examples/basic/noteon2osc.py