The Collaborative International Dictionary of English v.0.48:

Volta \Vol"ta\, n.; pl. Volte. [It. volta a turn, turning, a
   time. See Volt a tread.] (Mus.)
   A turning; a time; -- chiefly used in phrases signifying that
   the part is to be repeated one, two, or more times; as, una
   volta, once. Seconda volta, second time, points to certain
   modifications in the close of a repeated strain.
   [1913 Webster]