alto vs singer

alto and singer both are nouns.

Word	Noun	Adjective	Verb	Adverb
alto	Yes	Yes	No	No
singer	Yes	No	No	No

As nouns, singer is a hypernym of alto; that is, singer is a word with a broader meaning than alto:

Other hypernyms of alto include vocaliser, vocalist, vocalizer.

alto (noun)	singer (noun)
the pitch range of the lowest female voice	a person who sings
(of a musical instrument) the second highest instrument in a family of musical instruments
the lowest female singing voice
the highest adult male singing voice
a singer whose voice lies in the alto clef

alto (adjective)	singer (adjective)
(of a musical instrument) second highest member of a group
of or being the highest male voice; having a range above that of tenor
of or being the lowest female voice