It says a lot about what kind of “rock stars” Pink Floyd were that, after The Dark Side of the Moon ushered them from artsy Euroflick soundtrack cult heroes to ultramegablockbuster status, their next move was to cut a record inspired by the man who couldn’t be there to join them in their success. Big-ticket LPs have rarely sounded so mournful, especially off the presence of the two-half, nine-part Syd Barrett tribute suite “Shine on You Crazy Diamond,” which unfurls like a take on the Isaac Hayes version of “Walk on By” set in an abandoned Brutalist spaceship factory. (Roger Waters’ alternately near-catatonic and panic-shouted vocals, combined with David Gilmour’s emotively plaintive metablues guitar playing, somehow both uncannily evoke Syd’s spirit without actually sounding like anything he ever did with the band.) Sentiment jostles with cynicism — “Have a Cigar” and its sour funk dredging up bad memories of early-career record label puffery, “Welcome to the Machine” the Eno-gone-dystopian consequence of signing on that dotted line — which only makes the title cut’s last-gasp-of-psych-folk saudade that much more of a dagger to the heart. Cathartic bummer trips are never easy, but this one gets you by the choked-up throat.