Is the Artist column in your iTunes Library cluttered with hundreds of artists you never heard of? You may be the victim of "compilations." A compilation album contains tracks by multiple artists. Examples include tribute albums, benefit concerts, and soundtracks. For example, the (mythical) album "One Hit Wonders of the 80's" might contain 25 tracks each by a different artist (that's why they were one hit wonders). If you downloaded this album, each artist would be listed in your Artist list, with one associated track.