Python 3 based implementation of an object-oriented API for controlling and monitoring some REAPER mixer features. Leverages the built-in OSC control surface so no additional DAW-side extensions are required. Works on Windows, macOS and Linux.

from reaper import Client as ReaperClient

def reaper_ready(reaper):
  reaper.mixer.get_track(1).volume = 6.0
  reaper.transport.play()

reaper = ReaperClient()
reaper.add_observer(reaper_ready, prop='ready')
reaper.connect()

• Transport play and record status
• Track volume, pan and mute
• FX bypass
• FX parameter values

• REAPER → Preferences → Control/OSC/web → Add → OSC → Mode "Local port"
• Add one or more tracks with some FXs
• Run example.py and follow instructions for a control demo
• Tweak volume, mute, plugins... for a feedback demo