There are at least 6 bands/artists with the name Troy:

Troy: Incorrect Name Of The Artist.
The most common use of Troy in Last.Fm, It's an incorrect tag to Zac Efron, So, Please, Do Last.Fm a favor and fix your tags.
Troy is character that actor Zac Efron plays in a musical movie.

Troy (The Band):
Troy is a Rock band from Springfield, MO that consists of Chris, Kane, Cord, and Johnny B. They've recently opened up for such bands as Breaking Benjamin, Three Days Grace, Skillet, Puddle Of Mudd, The Exies, Korn and much more! Their debut album «Effective Immediately» was released December 1st, 2007. The band is currently working on a new album due TBD.

Troy:
Hip‑Hop producer and co‑founder of BoomBox Union.

Troy (a Female Singer):
TROY is also a female singer that appeared on the Ghost in the Shell: Stand alone complex OST

Troy:
Troy is a Power Metal band from Moscow, Russia formed in 2005 under Musica Production.

Troy:
Troy is the alter ego of Hugo DeTroyer, a Belgian singer‑songwriter who makes world‑folk influenced songs.

Troy:
Troy is an electronic music DJ & producer from Missouri, USA