An eight or fifteen above a clef raises the intended pitch range by one or two octaves respectively. Similarly, an eight or fifteen below a clef lowers the pitch range by one or two octaves respectively. A treble clef with an eight below is the most commonly used, typically used instead of a C clef for tenor lines in choral scores. Even if the eight is not present, tenor parts in the treble clef are understood to be sung an octave lower than written.