Seems kind of perfect that a band that calls itself Sundown would return triumphantly from its cross-country “Rockwood to the Roxy” tour just a few minutes after, well, sundown on the longest, sunniest day of the year, right?

Sure, a thunderstorm raged outside just before the acoustic trio began its standing-room-only Rockwood Music Hall performance Thursday night (the summer solstice), but not even a grimy New York City downpour could dampen the band’s spirits.

The band — comprised of singer/songwriters Casey Shea, Wes Hutchinson and Andy Stocks — took the stage stoically, gathering in a tight semi-circle around a single microphone. The trio opened with a spine-tingling, three-part, a capella intro to “In the Morning,” then began its hour-long, velvet-gloved assault on all that is slick, cynical, or artificial.

What distinguishes Sundown (and much of the musical community sprung up around Rockwood Music Hall founder Ken Rockwood’s intimate Lower East Side venue) is its anachronism in the pop-culture strata. Sundown’s songs, while not derivative, are reminiscent of a hazy, lazy, bygone era before Pro Tools, drum loops, remixes or mash-ups. Grounded by acoustic guitars and lush harmonies and adorned with only the occasional harmonica or shaker, the band’s music sounds like something one would hear wafting from a front porch somewhere in Laurel Canyon circa 1974. They’re the Lost Boys of Crosby, Stills & Nash.

Moreover, like Joni Mitchell’s “California” and Led Zeppelin’s “Going to California,” songs like “West Coast Callin’” and “Maybe Denver” demonstrate the band’s guileless mythologizing of the American West. Instead of being cloying or quaint, though, the band’s earnestness makes it refreshing and endearing.

It was apparent that the guys had spent the last six weeks traveling, performing and recording together (chronicled in the band’s blog) as they traded casual smiles, winks and nods throughout the set. And it was apparent that the audience was starved for the band’s brand of substantive authenticity as it emphatically called out for an encore. The band delivered with “Youth Is Wasted on the Young,” returning the room to hushed reverence.

The club was suspiciously populated by thirtysomething A&R types, leading one to believe that these intimate Rockwood performances might not last much longer. For the boys of Sundown, one can only hope as much.