Turns off all notes that were turned on by received Note On messages, and which haven't yet been turned off by respective Note Off messages. This message is not supposed to turn off any notes that the musician is playing on the local keyboard. So, if a device can't distinguish between notes played via its MIDI IN and notes played on the local keyboard, it should not implement All Notes Off. Furthermore, if a device is in Omni On state, it should ignore this message on any channel.
Note: If the device's Hold Pedal controller is on, the notes aren't actually released until the Hold Pedal is turned off. See All Sound Off controller message for turning off the sound of these notes immediately.
The value byte isn't used and defaults to 0.