'Transpose notes and chords in this LeadSheet.
All notes and chords are transposed the specified amount. Additionally,
all notes are octave shifted to lie within the [min_note, max_note) range.
Args:
transpose_amount: The number of half steps to transpose this
LeadSheet. Positive values transpose up. Negative values
transpose down.
min_note: Minimum pitch (inclusive) that the resulting notes will take on.
max_note: Maximum pitch (exclusive) that the resulting notes will take on.'

def transpose(self, transpose_amount, min_note=0, max_note=128):

    self._melody.transpose(transpose_amount, min_note, max_note)
    self._chords.transpose(transpose_amount)
