midi_all_notes_off  
Sends a MIDI all notes off message to all connected MIDI devices. on all channels. Use the port: and channel: opts to restrict which MIDI ports and channels are used.
When an All Notes Off event is received, all oscillators will turn off.
MIDI 1.0 Specification - Channel Mode Messages - All Notes Off
Introduced in v3.0
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| # Example 2 | |
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