Why in Arduino Due works only 34 pins at once?

Hello, please help me with arduino Due with libraries "MIDIUSB.h" and "PitchToNote.h". Why always work only 34 pins? It not depends which, but alway work only 34pins. for example 0-33 pin or 2-35 pin or it not depends. Please, Do you know why? Sorry for my bad english. Thank you