Most musicians are familiar with the treble clef and the bass clef, but they may sometimes see a different clef in printed music, including the alto clef, percussion clef, tenor clef, or treble octava bassa clef. While many liturgical musicians won’t be reading music in these clefs, it’s helpful to know a simple explanation for what they are and when they’re used.

Alto clef

The alto clef is the standard clef for the viola, and may also be used for the alto vocal part of a choral piece with multiple parts, including SATB, SSAA, and others. In a string quartet, the viola functions as the third voice among four parts – violin 1, violin 2, viola, and cello.

The alto clef exists because the viola and the alto vocal parts tend to have relatively common- pitches below Middle C, also known as C4 because it’s the C in the 4th octave on a piano. Thus, having a clef where C is the center line allows for more of the notated pitches to fall on the standard five lines of the staff. If the same vocal or string part was written in treble clef, then many notes would be on ledger lines below the staff and the singer/player would have to mentally keep track of where the pitches fell, as opposed to memorizing that C was the center line and F was the lowest line and so on.

Compare the two following examples where the exact same notes are notated on the different clefs.

Percussion clef

In some octavos, a liturgical musician might see a line written for unpitched percussion using a percussion clef. This clef can be used with any number of staff lines, though typically a single line or a standard five-line staff are used.

The percussion, or neutral, clef is used to notate rhythm for unpitched instruments like a tambourine, maracas, claves, or a hand drum.

Tenor clef

The Tenor clef is used in a similar way as the alto clef, just adjusted slightly. This clef is rarely used in modern music notation, but it may be present in older publications.

Treble octava bassa clef

The treble octava bassa clef (Italian for the treble down eight clef) is usually used to notate the tenor vocal part of an SATB score or octavo. While tenors read their parts as if on the treble clef, the pitches of mature tenor voices will sound an octave lower. Thus, what looks like a G above middle C is actually a G below middle C. Some liturgical music will use this notation to indicate the correct sound of the treble voices, while other liturgical music may not.

As you can see from these brief explanations, most liturgical musicians won’t encounter these uncommon clefs, except in the occasional choral piece where an alto clef or treble octava bass clef may be used. A viola player in a liturgical ensemble may encounter the alto clef when playing from a part written specifically for viola, but they may also simply read from the tenor line for many of their parts.

Even for vocalists and instrumentalists who don’t regularly encounter these clefs, it’s helpful to know they exist and where they may be used as part of understanding music theory.

Written by Ray Mullins, a CLEF volunteer who has served in music ministry and music education for two decades. He is a music teacher in Tennessee and volunteers as a music minister in various parishes in the Memphis area.

Copyright © 2026 Catholic Liturgical Ensemble Formation.

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