What is an alto singer. Alto clef (Mus.) the counter-tenor clef, or the C clef, placed so that the two strokes include the middle line of the staff. Moore called?

alto — An alto singer. Alto clef (Mus.) the counter-tenor clef, or the C clef, placed so that the two strokes include the middle line of the staff. Moore. (Webster's 1913.)

Sources