Adafruit USB MIDI does not create device

Projects Programming
3

Actually, the provided example does not compile. I had to add:

void handleNoteOn(byte channel, byte pitch, byte velocity);
void handleNoteOff(byte channel, byte pitch, byte velocity);

before the setup() otherwise it cannot find the functions (declared below).
About the MIDI the original code works:

$ aseqdump -l
 Port    Client name                      Port name
  0:0    System                           Timer
  0:1    System                           Announce
 14:0    Midi Through                     Midi Through Port-0
 32:0    BPI-Leaf-S3                      BPI-Leaf-S3 MIDI 1

I wonder what is my mistake in my code.