If you want to change the object from "All Notes Off" to "All Sound Off", you can tweak the plugin code by changing the following line:
nwcplay.midi(0, 'controller', 123, 0)
to:
nwcplay.midi(0, 'controller', 120, 0)
From the replies I have seen so far, it sounds like a more general version of the plugin would be useful. I'll work on a version that lets you pick the kind of message you want to send. In the meanwhile, let me know if "all sound off" works for your case. However, please note that these MIDI messages are channel specific, and will only send for the current staff's instrument channel.