Although the viola is tuned in concert pitch (or “C“), not only is the music for this instrument written in an unusual clef, it shares a range with many instruments that are not in concert pitch. For this reason, reading viola music on other instruments often requires several steps in transposition, steps that must be taken carefully in order to avoid the harsh clashes of out-of-key playing.
Identify the notes by reading alto clef notation. Alto clef is a movable clef, which means that the position of middle “C” changes, but is always designated as the center line where the upper and lower halves of the clef’s curly design meet. Most of the time, this is also the center line of the five-line staff.
Transpose the notes to bass or treble clef for “C” instruments. On bass clef, the “C” of the alto clef’s center line is the same as the “C” located one leger line above the staff. On treble cleff, this “C” is located one leger line below the staff. Adjust all intervals accordingly to make the relative distances between the notes the same.
Arrange the notes for instruments pitched in different keys. Bear in mind that the name of the instrument’s pitch indicates which written pitch sounds as a standard “C” for that instrument. For example, when transposing for a Bb trumpet, the alto clef “C” will become a Bb. Adjust all intervals to match this change.
Choose octaves for your music, if necessary. The viola plays in a middle register, which may make some of the notes in the higher ranges of a piece of music too high for a tenor instrument, while some of the lower notes will likely be too high for a soprano instrument. For bass or sopranino instruments, you can usually transpose all of the music down or up one octave, respectively.
Transpose the key signature. For other “C” instruments, this is as simple as writing it in the new clef. For other instruments, find the tonic in the transposed melody and write the key signature for that pitch.