MIDI All Notes Off vs All Sound Off: The Difference

While both MIDI commands are designed to silence unwanted or hanging audio on a specific channel, the fundamental difference lies in how the sound terminates. MIDI "All Notes Off" (CC 123) functions like releasing all held keys simultaneously, allowing active notes to fade out naturally through their programmed release stage. In contrast, MIDI "All Sound Off" (CC 120) acts as an immediate hard mute, cutting off all sound generation instantly and bypassing any amplitude envelopes.

What is MIDI All Notes Off (CC 123)?

MIDI Control Change (CC) 123 sends a command that simulates a "Note Off" message for every currently active key on that specific MIDI channel.

• Envelope Behavior: Because it behaves like physically releasing keys on a keyboard, the synthesizer's amplitude envelope proceeds to its normal "Release" phase. If an instrument has a long release time (like a swelling pad or a sustained string patch), the sound will continue to ring out and decay naturally.
• Sustain Pedal Interaction: On many devices, if the sustain pedal (CC 64) is currently engaged, the sound will continue to hold even after CC 123 is sent, waiting until the sustain pedal is released before decaying.
• Best Used For: Clean musical transitions, resetting hanging keys during a live performance without creating an abrupt, jarring silence, or resetting note states between song sections.

What is MIDI All Sound Off (CC 120)?

MIDI Control Change (CC) 120 is an emergency command designed to silence a MIDI channel immediately.

• Envelope Behavior: CC 120 bypasses the release stage of the ADSR envelope entirely. The internal audio generators (oscillators, sample playback, or voice cards) are forced to an output level of zero without any delay or fade.
• Sustain Pedal Interaction: It overrides all controllers, including the sustain pedal. Even if the sustain pedal is physically held down, the sound terminates instantly.
• Best Used For: A true "panic button" function when notes are stuck indefinitely due to MIDI loopback errors, software crashes, or missing Note Off signals where you need immediate silence.

Summary of Differences

• Decay: All Notes Off allows the sound to decay naturally; All Sound Off cuts the audio instantaneously.
• Controller Override: All Notes Off respects the sustain pedal; All Sound Off ignores sustain and silences everything.
• Musicality: All Notes Off sounds natural and musical; All Sound Off causes an abrupt, noticeable click or cut in the audio stream.