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MIDI Merge Units


MIDI Merge Units

Have you ever needed to merge incoming MIDI data from different MIDI sources to one ( or more)  MIDI output? These MIDI Merge Units can be used to combine all MIDI messages appearing at the MIDI inputs onto the MIDI output connectors.


The 3 types of MIDI merge units available merge the data from two, three or four separate MIDI sources (e.g. Master keyboards or controllers) into a single MIDI data stream which appears at all of the MIDI out sockets. Merges all MIDI data including MIDI Clock, MIDI time code and SysEx.

Each design contains a suitably pre-programmed ATmega 2560 microcontroller board with up to 4 serial inputs and 4 serial outputs. Also each of the serial inputs have a MIDI IN/OUT board with opto-isolated MIDI Inputs and a MIDI Output.








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PRICE:  €65.00









PRICE:  €75.00






PRICE:  €85.00




The MIDI Merge Units utilize:


  • An assembled, built and tested Arduino board including a suitable pre-programmed microcontroller,
  • 2, 3 or 4 Opto-isolated MIDI IN/OUT boards,
  • A 2.1mm power socket, and associated LED, 
  • A MIDI detection LED,
  • A 150mm wired MIDI 5-pin DIN input socket,
  • A 150mm wired MIDI 5-pin DIN output socket, 



The MIDI Merge Units require:

  • A 9 Volt battery or equivalent 9 Volt DC external power source, or USB Connector.


Circuit Schematic Diagrams:






     *Click to Enlarge*

The MIDI IN and OUT connectors use  5-Pin 180 degree DIN sockets. Note that the MIDI IN/OUT wiring is polarised and the correct pins should be used.






The unit detects the incoming MIDI data from all the inputs merges the data streams and sends the combined MIDI inputs to all the MIDI outputs.


Unfortunately you cannot combine MIDI data streams just by joining the wires together. Data that arrived at the same time would clash and be corrupted into garbage. In addition, the 'bytes' of information must be organized according to the MIDI protocol. So merging MIDI data is a job for a microcontroller with multiple serial interfaces (one for each MIDI port).




Power Supply:

The  Arduino can be powered via the USB connection or with an external power supply. 


External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector. A low dropout regulator provides improved energy efficiency.


The board can operate on an external supply of 7 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.



A MIDI Merger has applications wherever you need to combine MIDI data streams. You may want to combine several simultaneous performances on the input of a computer or a sound module.


MIDI Specification: 

 The MIDI Channel Changer commands are all channel (1-16) dependent. The system will also work with MIDI running status. Here are details of the various MIDI Messages.