Hi Rob > what is the MIDI Thru used for? ..."Some instruments have a third MIDI jack labeled "Thru". This is used as if it were an OUT jack, and therefore you attach a THRU jack only to another instrument's IN jack. In fact, the THRU jack is exactly like the OUT jack with one important difference. Any signals that the instrument itself creates (or modifies) are sent out its MIDI OUT jack but not the MIDI THRU jack. Think of the THRU jack as a stream-lined, unprocessed MIDI OUT jack."...  Source: http://www.borg.com/~jglatt/tutr/whatmidi.htm Best Regards, Lemonhorse  :)