sightreader vs performer

sightreader and performer both are nouns.

Word	Noun	Adjective	Verb	Adverb
sightreader	Yes	No	No	No
performer	Yes	No	No	No

As nouns, performer is a hypernym of sightreader; that is, performer is a word with a broader meaning than sightreader:

sightreader: a performer who reads without preparation or prior acquaintance (as in music)
performer: an entertainer who performs a dramatic or musical work for an audience

Other hypernyms of sightreader include performing artist.

sightreader (noun)	performer (noun)
a performer who reads without preparation or prior acquaintance (as in music)	an entertainer who performs a dramatic or musical work for an audience