Learn Italian: Nessun pianista ha suonato stasera.

Words ending in -ista have the same form for masculine and feminine in the singular. We can tell this refers to a male pianist because it uses nessun (masculine). If it were a female pianist, it would be nessuna pianista.

Why is it nessun instead of nessuno?

As an adjective, nessuno follows the same pattern as the word un/uno. Since we say un pianista (a male pianist), we use nessun pianista. You only keep the 'o' before masculine words starting with 'z' or 's+consonant' (like nessuno studente).

Shouldn't there be a non in this sentence for a double negative?

In Italian, when negative words like nessun, niente, or mai come before the verb, you do not use non. If the sentence were flipped to put the subject after the verb, then you would need the double negative: Non ha suonato nessun pianista.

Why is "played" translated as ha suonato instead of ha giocato?

Italian uses different verbs for playing. Suonare (related to the word for "sound") is used exclusively for playing musical instruments. Giocare is used for playing sports, games, or playing like a child.