#define BEEPER 27 // Pin 27 is take by LED_Pin, but Melzi LED do nothing with Marlin and I take this pin for BEEPER.... See here > [github.com] , If you want use this pin with Gcode M42 instead BEEPER
#define BEEPER_PIN 27 // Pin 27 is taken by LED_PIN, but Melzi LED does nothing with Marlin so this can be used for BEEPER_PIN. You can use this pin with M42 instead of BEEPER_PIN.