 The use of different clefs for various instruments and voices allows each part to be written comfortably on the stave with a minimum of ledger lines.To this end, the G-clef is used for high parts, the C-clef for middle parts, and the F-clef for low parts—with the notable exception of transposing parts, which are written at a pitch different from their sound, often even in a different octave.To facilitate writing for different tessituras, any of the clefs may theoretically be placed on any line of the stave.