Learn Hardcore Latin: Fidicen citharam canit, et convivae eum libenter audiunt. - The lyre-player plays the cithara, and the guests gladly listen to him.

Fidicen is a noun meaning a stringed-instrument player or musician. In this sentence, because of citharam, it means the person who is playing the cithara.

Grammatically, fidicen is:

nominative singular
third declension
the subject of canit

So fidicen canit means the musician plays.

Why is it citharam and not cithara?

Because citharam is the direct object of canit.

Latin marks the direct object with the accusative case. For a first-declension noun like cithara, the accusative singular ends in -am:

cithara = nominative singular
citharam = accusative singular

So:

cithara canit would not work for this meaning
citharam canit = he plays the cithara

Does canit mean sings or plays?