This double CD is a true gift to hardcore fans, offering previously unseen glimpses of Jethro Tull when the group was at its absolute peak. Anyone else, however, may find the album rough going, for while the group was never tighter or more productive, the material isn't even second-rate. Essentially, Nightcap is Jethro Tull's version of the Beatles' Anthology releases. The first disc consists of tracks that the band started to record during 1973 – the best parts of this material ended up being rewritten and incorporated into what became A Passion Play. These outtakes are pretty at times, but also unformed and distinctly unfinished – Anderson takes a gorgeous classical guitar solo on "First Post," but then the song drifts off, and "Tiger Toon" is an early version of the principal theme from "A Passion Play," not altered too much except in tempo.