Using the MIDI library in my own library
void MIDI_CREATE_DEFAULT_INSTANCE();


This line should not be placed inside a function, because it is a forward function declaration.

However, I think there are more problems in your code.

My wild guess is to improve the following lines:


Uncomment line that doesn't work


Change

MIDI_CREATE_DEFAULT_INSTANCE();


to

MIDI_CREATE_DEFAULT_INSTANCE();


and place it outside a function.

Remove the word void  in the following lines

void midiSetup();
void pmbMIDI();


And also align the { and } 

void MIDI.begin(MIDI_CHANNEL_OMNI);


So it's a function call.

Other improvements is to remove spaces or tabs  in

    void midiSetup();
    void pmbMIDI();


Also align { and } in

if (MIDI.getType() == 144){
    digitalWrite(13, 1);}

if (MIDI.getType() == 128){
    digitalWrite(13, 0);}