Formerly the part sung by the highest male, or counter-tenor, voices; now the part sung by the lowest female, or contralto, voices, between in tenor and soprano. In instrumental music it now signifies the tenor.
(Ital.) : (1) The second highest of the four customary voice parts, below the soprano and above the tenor. (2) Singer with that vocal range. (3) [in scores] Viola. The term alto is also used to describe models of the flute and clarinet lower than the usual one; the alto saxophone is the most common of the saxophones, though there is a soprano saxophone.