Sometime in the early 1970s, Frank Zappa wearily stated during a TV interview that average rock fans generally liked music they didn't have to try too hard to fathom — "Nothing too off-the-wall," FZ said in the parlance of the time. If the recordings comprising Wazoo had been released when recorded — 1972 — it's unlikely it would have won Zappa too many converts from the mainstream rock audience. Recorded live in Boston, Wazoo features selections from Zappa's 1973 album The Grand Wazoo and other material that was too off-the-wall to see daylight until the late '70s (on albums such as Studio Tan). This two-CD set features some of Zappa's most challenging compositions, performed by his short-lived touring orchestra. There are no vocal selections, and the man's legendary satirical wit is expressed purely in an instrumental context. The tunes "Approximate" and "Big Swifty" present whimsical and knotty arrangements while "Penis Dimension" and "Variant I Processional March" are closer in essence to Zappa's classical compositions. If you're familiar with 20th-century composers like Charles Ives and Igor Stravinsky, it'll all make sense. The 32-minute ditty "The Adventures of Greggery Peccary" finds those influences (and more) completely integrated into Zappa's approach. Further, many of the horn soloists get to engage in some bracing, envelope-pushing, free-jazz playing. Wazoo is not really for the casual Zappa fan but for the devotee — and younger listeners weaned on post-rock such as Tortoise and Rachel's — it's as essential as food and water.