Learn Italian: Il batterista non sa che cosa fare senza lo spartito. - The drummer does not know what to do without the sheet music.

This is an implicit indirect question, which is exactly what this lesson covers! When the subject of the main verb (the drummer) is the same as the implied subject of the action (what he should do), Italian pairs a question word like che cosa directly with an infinitive like fare. It translates perfectly to the English structure "what to do."

Could I just say cosa fare instead of che cosa fare?

Yes, absolutely. When meaning "what," Italian allows you to use che cosa, just cosa, or just che. Cosa fare is actually very common in spoken, everyday Italian, while che cosa fare is considered the most grammatically complete and traditional form.

Batterista ends in -a, so why does it use the masculine article il?

Words ending in the suffix -ista that refer to professions or roles (like batterista, dentista, or turista) are identical for both masculine and feminine. The article is what tells you the gender of the specific person. Here, il batterista tells us the drummer is male. If the drummer were female, it would be la batterista.

A quick refresher: why is it lo spartito instead of il spartito?