midi_sound_off  
Sends a MIDI sound off message to all connected devices on all channels. Use the port: and channel: opts to restrict which MIDI ports and channels are used.
All oscillators will turn off, and their volume envelopes are set to zero as soon as possible.
MIDI 1.0 Specification - Channel Mode Messages - All Sound Off
Introduced in v3.0
| # Example 1 | |
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| # Example 2 | |
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