useless trivia: What Word Means: A Mathematical Set?

Questions

Covers: This hard-to-find Metallica release contains nothing but covers:?

Covers: This new band performs a cool cover of Hey Hey What Can I Do by Led Zeppelin:?

Covers: This punk band did an infamous cover of "My Way":?

Covers: Vanilla Ice's _Ice Ice Baby_ sounds a lot like this David Bowie/Queen song:?

Critics say the Beach Boys are a "pale shell" of themselves since he died.?