Even at age 72, quintessential soul diva Patti LaBelle knows only one way to sing — all out. And at Proctors on Saturday night, she didn't hold anything back. She left it all out in the spotlight. She steamed up the ballads, notably "If You Asked Me To" and "Little Girls," the latter accompanied only by musical director John Stanley at the white grand piano. Backed by her full seven-piece band and three backing vocalists, she tore into the upbeat dance party selections, including the opening "Feels Like Another One" and, of course, the disco classic "Lady Marmalade," during which she brought a number of members of the audience up onstage to strut their stuff, singing and dancing with her. She served up steely determination on anthems like "On My Own" and her show-closing medley — the unlikely mash-up of Harold Arlen's "Somewhere Over the Rainbow" and R. Kelly's "I Believe I Can Fly." And she simply poured her heart out during the back-to-back pairing of the gospel gems, "When You've Been Blessed" and "Every Praise." She's been singing for more than a half-century: with girl group the Bluebelles in the '60s; the spacey soul-rock trio LaBelle in the '70s; and as a hit solo artist since 1977. And she knows how to reach out and touch an audience directly, without artifice. She loves her fans, and they love her right back with a fervor and devotion that precious few performers ever enjoy, let alone maintain throughout a career that's stretched on for so many years.