An expanded reissue of Fleetwood Mac's underrated 1979 double album Tusk is on the way. Available in a variety of formats on Dec. 4, the set promises to shed to new light on the group's most ambitious project.

Tusk ended up selling more than four million copies, reaching No. 1 on the U.K. album charts behind favorites like "Sara," the title track and "Think About Me." Still, in following the blockbuster Rumours, that was considered a disappointment in some circles. The Grammy-nominated album's more experimental touches also confused a faction of newer fans.

It's all explored across a forthcoming 5CD/1DVD/2 LP deluxe edition of Tusk, which will also be available in a 3CD expanded edition, and a 1CD remaster.

The deluxe version includes the original remastered music, an alternate version of the complete album substituting session outtakes – most of which are previously unheard – as well as singles, demos and remixes. Highlights include an early version of "That's Enough for Me," which was then titled "Out on the Road." Two additional discs focus on performances from Fleetwood Mac's 1979 dates in support of Tusk, recorded in London, St. Louis and Tuscon. This edition is completed with a 5.1 surround mix on DVD-audio, a two-disc vinyl set, and an elegant booklet with expanded liner notes and new interviews.

The expanded edition includes the remastered original album, the alternate edition of sessions outtakes, as well as the singles, demos and remixes. Meanwhile, the reunited Tusk-era lineup continues a hugely successful world tour. Lindsey Buckingham, Mick Fleetwood, Christine McVie, John McVie and Stevie Nicks recently sold out six shows at the O2 Arena in London.

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