Build your own MIDI circuits
Frequently Asked Questions.
MIDI & Music
MIDI and Music Information
MIDI 6 Octave Transposer


MIDI 6 Octave Transposer


This octave shift transposer can be used to extend the note range for a small note range MIDI keyboard or pedalboard.


The MIDI 6 Octave Transposer is used to transpose an incoming MIDI note by up to 3 Octaves above or down to 3 Octaves below, by an octave each time one of the switches is pressed. That octave selection is stored until one of the switches is pressed again. When the unit is powered on the octave selection resets to 0.


It is MIDI Channel (1 to 16) dependent. So it affects only the single selected MIDI Channel, the other 15 channels pass through the circuit unaffected. The MIDI Channel is selected by the settings in a 4-way DIL switch.


*Click to Enlarge*


MIDI 6 Octave Transposer


PRICE:  €50.00






The MIDI 6 Octave Transposer unit utilizes:


  • An assembled, built and tested Arduino board including a suitable pre-programmed microcontroller,
  • A MIDI IN and OUT board,
  • 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 complete circuit schematic is available,
  • The MIDI IN/OUT circuit schematic is also available.



The MIDI 6 Octave Transposer requires:

  • A 9 Volt battery or equivalent 9 Volt DC external power source, or USB Connector,
  • 2 momentary action push button switches.








     *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 2 momentary action switches increase or decrease the incoming MIDI note by an octave each time they are pressed.  They are limited to a maximum of +/- 3 octaves. Also the combination of incoming MIDI note and the octave shift are limited to the MIDI note range of 0 to 127.



The unit detects the incoming MIDI data, and all other MIDI Channel commands and data are transferred from the MIDI IN to the MIDI OUT socket unchanged.





MIDI Channel (1 to 16) Selection Table:



DIP Switch Selections



4 3 2 1
on on on on 1
on on on off 2
on  on  off on 3
on on off off 4
on off on on 5
on off on off 6
on off off on 7
on off off off 8
off on on on 9
off on on off 10
off on  off on 11
off on off off 12
off off on on 13
off off on off 14
off off off on 15
off off off off 16

Table 1 MIDI Channel



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.