multimedia keys:
F3: Previous track
F4: Play/pause
F5: Next track
F9: Mute
F10: Volume down
F11: Volume up
turn off: hold equal (=) and press p (for PC).
turn off: hold equal (=) and press w (for windows).
turn off: hold equal (=) and press m (for Mac).
turn on: hold equal (=) and press n.
to see what your keys are sending:
acpi_listen