You’d be right to be skeptical of Columbia’s newest round of vault cleaning. But it would be foolish not to hear Live at Winterland ’68 as roaring testimony to Joplin and her band at the height of their powers. Whereas Cheap Thrills was largely a studio album tricked up to create the illusion of a concert recording, this CD yields 75 minutes from two genuinely live concerts. Joplin rushes the vocal on “Down on Me,” and her rendition of “Ball and Chain” is better on Cheap Thrills, but her very tentativeness and her daredevil spirit of experimentation on this 1968 recording is fascinating. Never the most subtle of blues belters, the Joplin who shows up on Winterland is refreshingly free of the mannerisms that became legend on her later studio albums. And her backing band? Sloppy, yes, but Sam Andrew’s psychedelic guitar noodlings still communicate urgency and whimsy, the sound quality is pleasantly clear for the time and place, and the extensive liner notes all make this an essential collection for fans of ’60s rock.