(Italian: “high”), in vocal music the register approximately between the F below middle C to the second D above—the second highest part in four-part music. The word alto originally referred to the highest male voice, singing falsetto (see countertenor).

Alto derives from the term contratenor altus, which in Renaissance music referred to the part immediately above the tenor part. Female alto voices are often called contralto. The term alto is also used for musical instruments having a more or less comparable range—e.g., alto saxophone, alto clarinet, alto flute. The meaning of alto in French is “tenor violin” or “tenor saxhorn”—a pitfall for translators; contralte in French means the English “alto.”