The MIDIBox AY has no Encoders or Buttons - but a C64 Keyboard.
The C64 Keyboard must be connected to the MBHP DOUT (DOUT1: J3(Pin D0 to D7)) Board and MBHP DIN (DIN1: J3/J4(Pin D0 to D7)) Board
See DOUTX4 ⇒ http://ucapps.de/mbhp/mbhp_doutx4.pdf
See DINX4 ⇒ http://ucapps.de/mbhp/mbhp_dinx4.pdf
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See also MidiBoxKB by bill ⇒ midiboxkb_-_using_a_c64_keyboard_as_input