Was I lying when I called Dianne Reeves one of the greatest jazz singers ever in my preview article for her Isthmus Jazz Series concert? I don't think anyone in Friday's ecstatic audience at Wisconsin Union Theater would have indicted me. With her uncannily flexible voice, Reeves turned every song into a tour de force. Heck, she could even turn individual words into a tour de force, breaking them into scales, hopping crazy intervals, and never landing on the note you expected her to land on. Reeves matched her idol, Sarah Vaughan, in virtuosity, and that's saying a lot. But thankfully, virtuosity wasn't the point. Expressiveness was, with Reeves' technical skill serving as the means to an end. With help from an extraordinarily sympathetic quartet -- pianist Peter Martin, bassist Reginald Veal, guitarist Romero Lubambo and drummer Terreon Gully -- she rendered subtle moods on original songs and standards like "Stormy Weather." With her beaming smile and occasional dance moves, Reeves gave the impression of enjoying herself greatly. "This isn't a stage," she said, sashaying in a white silk dress. "It's really a playground." Man, was it ever. Reeves got big laughs telling a story of an old crush in between verses of the Temptations' "Just My Imagination," which retained its R&B groove despite her baroque recasting of the melody. During a slinky Latin song, she cheered on a couple who were moved to dance in the aisle. "If it makes you want to move, go ahead and groove," she spoke-sang in the middle of her performance. As Reeves scatted through a typically original take on George Gershwin's "Our Love Is Here to Stay," her guitarist broke into a huge smile, his mouth hanging open. Even though he's been playing with her since the 1990s, he seemed thunderstruck by her talent. I knew how he felt.