What do the MIDI in and MIDI out buttons do?

Switching on the MIDI Out button causes MIDI events to be sent when they are added, selected, or edited. This allows you to audibly monitor every editing stage.

When the MIDI Out button is off you won't hear any selection, adding, or editing.

MIDI In button has three modes: Off, solid white, and white silhouette.

When the In button is solid, you can insert notes via an external MIDI keyboard (it will follow your Division setting). You can use the Step Input Keyboard window and/or the Input key commands to adjust any settings that are not available from the MIDI keyboard itself.

When the MIDI In button is a white silhouette you can edit selected notes via an external MIDI keyboard.

Engage the MIDI in button and you can step enter MIDI notes - with Musical Typing or any MIDI Keyboard or MIDI pads. Step size depends on snap settings, I think.The MIDI out button on means that selecting a MIDI note will also play that note. Turn it off for silent selecting.