/ ˈæltəʊ; NAmE ˈæltoʊ/ noun , adjective
■ noun ( pl. -os )
1.
(also con·tralto ) [ C ] a singing voice with a lower range than that of a soprano ; a person with an alto voice
2.
[ sing. ] a musical part that is written for an alto voice
—compare baritone , bass , counter-tenor , tenor
■ adjective
[ only before noun ] ( of a musical instrument ) with the second highest range of notes in its group :
an alto saxophone
—compare soprano , tenor
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WORD ORIGIN
late 16th cent.: from Italian alto (canto) high (song).