alto vs high-pitched

alto is a noun but high-pitched is not a noun.

Word	Noun	Adjective	Verb	Adverb
alto	Yes	Yes	No	No
high-pitched	No	Yes	No	No

alto (noun)	high-pitched (noun)
the pitch range of the lowest female voice
(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)	high-pitched (adjective)
(of a musical instrument) second highest member of a group	used of sounds and voices; high in pitch or frequency
of or being the highest male voice; having a range above that of tenor	set at a sharp or high angle or slant
of or being the lowest female voice