Lexicon MRC V4.0 Owner's Manual Addendum page 52

MIDI data from the input port which is not connected to the LXP-1 can be
merged with the data on the output port used for two-way communication.
This is useful when you are using an LXP-1 register that uses MIDI sources
for patching. Merging functions are selected on page 1 of the SYSTEMS
PARAMETERS menu. The different merging options are outlined in the
following table:
Merging Options for Two-way Communication
IN1 -> OUT1 <ON/OFF>
IN1 -> OUT2 <ON/OFF>
IN 2 -> OUT2 <ON/OFF>
IN2 -> OUT1 <ON/OFF>
5-2
Lexicon MRC V4.0/ MIDI Remote Controller
Must be set to "OFF" if IN1/OUT1 are being used for
two-way communication with the LXP-1.
If IN2/OUT2 are being used for two-way communi-
cation with the LXP-1, any combination of MIDI
controllers, Pitch Bend, Aftertouch, Note numbers
and Program Change messages received on IN1
can be merged with MIDI OUT2 by setting this to
"ON".
Must be set to "OFF" if IN2/OUT2 are being used for
two-way communication with the LXP-1.
If IN1/OUT1 are being used for two-way communi-
cation with the LXP-1, any combination of MIDI
controllers, Pitch Bend, Aftertouch, Note numbers
and Program Change messages received on IN2
can be merged with MIDI OUT1 by setting this to
"ON".