def transpose(self, semitone):
        """
        Transpose the pianorolls of all tracks by a number of semitones, where
        positive values are for higher key, while negative values are for lower
        key. The drum tracks are ignored.

        Parameters
        ----------
        semitone : int
            The number of semitones to transpose the pianorolls.

        """
        for track in self.tracks:
            if not track.is_drum:
                track.transpose(semitone)
Transpose the pianorolls of all tracks by a number of semitones, where
        positive values are for higher key, while negative values are for lower
        key. The drum tracks are ignored.

        Parameters
        ----------
        semitone : int
            The number of semitones to transpose the pianorolls.