How to sort out your MIDI connections

MIDI connections convey serial digital signals, and you cannot combine these signals by joining wires together. The signals are carried by what is called a current loop; all MIDI connections must be one input to one output – inputs cannot reliably be ganged in series or parallel. You can deal with these limitations by using MIDI Merge Units and MIDI Thru Units.

A MIDI Merge Unit (merger) has applications wherever you need to combine MIDI datastreams. You may want to combine several simultaneous performances on the input of a computer or a sound module. You may want a MIDI Merge Unit to run a computer patch-editor to a synth-module at the same time as playing the module from a keyboard. You may want your MIDI Merge unit to insert MIDI synchronization (MIDI clocks or Time Code) into a performance datastream.

Little 2M, 2M, 3M, 5M and 9M MIDI Merge Units – Philip Rees products
MIDI merge - combining MIDI datastreams – quick info page

MIDI Thru Units (splitters) provide outputs which are copies of the signal arriving at their inputs. They allow a single MIDI Out port to drive several MIDI In ports at the same time. This avoids the signal corruption caused by long MIDI chains, and means that you do not need to keep all the slave units powered-up.

V3, V4, V8, V10 and W5 MIDI Thru Units – Philip Rees products
MIDI thru and MIDI thru boxes – quick info page

MIDI Selectors (switch boxes) let MIDI signals be sent along one of several routes, simply by moving a switch. These products need no power supply. They are also inherently bidirectional, so can be used as source selectors (one of several inputs to one output) or destination selectors (one input to one of several outputs).

2S, 5S, 9S and 3B MIDI Selectors – Philip Rees products
Simple switches for MIDI routing – quick info page

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