I'd like to know the best place for the button handler and how to get/set kb_transpose values. Here is some pseudo code. void APP_Background(void) { int old_transpose = kb_transpose; int new_transpose; // up btn pressed if( MIOS32_BOARD_J5_PinGet(0) == 0) { new_transpose = old_transpose + 12; } // down btn pressed if( MIOS32_BOARD_J5_PinGet(1) == 0) { new_transpose = old_transpose - 12; } // transpose and handle LEDs if( old_transpose != new_transpose ) { kb_transp