musician vs cantor

musician and cantor both are nouns.

Word	Noun	Adjective	Verb	Adverb
musician	Yes	No	No	No
cantor	Yes	No	No	No

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

musician (noun)	cantor (noun)
artist who composes or conducts music as a profession	the official of a synagogue who conducts the liturgical part of the service and sings or chants the prayers intended to be performed as solos
someone who plays a music as a profession	the musical director of a choir