MIDI Panic (Send All Notes Off)

1. Press both the Octave Down (7) and Octave Up (8) buttons simultaneously.
2. This sends 'All Notes Off', 'All Sounds Off', and 'Sustain Pedal Off' on all 16 MIDI channels.

Source: Xboard 25 — emu-xboard-25-49-61-manual-eng (manual)