accidental

a musical symbol (sharp, flat, natural, double sharp, or double flat) that appears before a not to raise or lower its pitch chromatically.

 clef

a symbol that appears on the far left of every staff to designate which line or space represents which pitch (in which octave).

alto clef

a c-clef positioned on a staff so that the middle line indicates middle C (C4); typically read by violas.