“The Wrecking Crew” is so Los Angeles-centric that the British Invasion barely registers. And although Mr. Hartman makes respectful note that outfits like Motown’s Funk Brothers (the subject of the rousing documentary “Standing in the Shadows of Motown”) were performing similar unsung heroics in other music meccas, his focus is simple and narrow. “The next time you listen to some of your favorite groups from the ’60s, please don’t be upset,” he cautions. “I never knew it was really the Wrecking Crew either.”

Among the jukebox triumphs that are celebrated here are “Limbo Rock,” a song so simple that Billy Strange, who wrote the music and called it “just about the dumbest thing I’ve ever heard,” was surprised to receive royalties for it; “The Beat Goes On,” the Sonny and Cher one-chord wonder that was such a bore for musicians to play; “River Deep, Mountain High,” with a Phil Spector Wall of Sound so messy that Wrecking Crew members hated being drowned out by it; and “Eve of Destruction,” which wound up on the radio before its singer, Barry McGuire, could do an adequate vocal. “Eve of Destruction” was a big hit in its own right, but it becomes even bigger when Mr. Hartman explains how it brought Lou Adler, the producer, together with four of his impecunious unknown friends: the Mamas and the Papas. Their records show off Wrecking Crew professionalism at its best.

For all Mr. Hartman’s efforts to clarify the mysteries of which musicians played on which records, the subject remains confusing. The Wrecking Crew was informal and had many members. Stars of the Wrecking Crew played on so many songs that they themselves haven’t all kept close track. It would take a whole other book to trace their individual trajectories. (There are other books. Mr. Hartman draws heavily on volumes about both Mr. Blaine and Mr. Spector.) But “The Wrecking Crew” does its job of commemorating studio heroics. It makes good music sound better.