saxophonist vs altoist

saxophonist and altoist both are nouns.

Word	Noun	Adjective	Verb	Adverb
saxophonist	Yes	No	No	No
altoist	Yes	No	No	No

As nouns, altoist is a hyponym of saxophonist; that is, altoist is a word with a more specific, narrower meaning than saxophonist:

Other hyponyms of saxophonist include alto saxophonist, tenor saxophonist, tenorist.

saxophonist (noun)	altoist (noun)
a musician who plays the saxophone	a musician who plays the alto saxophone