The full story of the anti-Sgt. Pepper (actually made a year before its release in 1967) is told over six CDs that stand up to the repetition (mono, stereo and alternate versions). The January '66 rehearsals are rough audio but key history: the Velvets in embryo, shortly after mentor Andy Warhol first saw them play. The two live discs from late '66 (long booted) are the classic lineup, with the icy blond Nico, at an avenging black-drone peak.
Listen to 'The Velvet Underground & Nico: 45th Anniversary Super Deluxe Edition':