analog organ by Cantor. Because they had a serious breakdown some time ago, they were converted into a MIDI console for controlling software like VPO (virtual pipe organ). Then, however, only the manual keyboards (manuals) and the pedal keyboard were connected through two interfaces constructed on the ATMEL89S52 chip connected to two separate MIDI outputs, one on the right and one left under the keyboard. It was a cost effective solution, but quite a hassle to connect a computer with GrandOrgue (aka Hauptwerk). You had to use two cables and two MIDI-USB interfaces or one double. In addition, the board with registers and group registers were not connected at all. Organ voices had to be changed on the monitor screen. The computer and monitor with GO had to be placed outside the organ, which also reduced the comfort of the game and took up space. I decided to connect the registration switches and group registries, and hide the computer inside the wooden casing of the organ. If it were possible to enable voices with registers and the GO was started from autostart, the screen monitor would be redundant and could be dispensed with. Ultimately, connect it only when changing the software configuration. I decided to use the Arduino Nano to connect the registers. I wrote the program in the Arduino IDE using the Surface_Controll (tappa) library. In order to connect 39 switches to a limited number of Arduino Nano pins, I needed to create a matrix with diodes. In this case, it was relatively easy to construct the matrix in the organization of 4 columns on the 14th row (3 panels of register switches plus switches for ten group registers). The matrix columns were attached to the pins 13, A5, 3, 2 and lines up to 4, 5, 6, 7, 8, 9, 10, 11, 12, A0, A1, A2, A3, A4. In order for pin 13 to work in matrix mode, you had to desolder the LED that is standard in the Arduino Nano on this pin.