Age has only improved the national treasure that is Sheila Jordan. The human voice deepens naturally over time, and this has softened the pinched timbre that sometimes characterized her earliest recordings, more than 40 years ago. As she approaches 80, her voice, like an Amati violin, has not only grown mellower but seems, improbably, even more responsive to her well-chosen whims and admirable fancies. Perhaps no other jazz singer has exploited the malleability of the instrument so flamboyantly: singing an up-tempo standard, Jordan riffs off the melody, preferring sensuous glissandi and touches of sprechstimme, and on a ballad solo her trademark gestures–an upswept fifth that plummets to a minor second, quarter-tone trills, hearty warbles–unmistakably evoke Native American chants. Many older singers draw on life experience to deepen their interpretations, hoping to compensate for the loss of technical flexibility; in Jordan’s case, wisdom enhances undiminished control. Listening to her sketch the theme of a ballad, you realize that her ability to dance around it with such hyperexpressive grace depends entirely on her precise awareness of pitch–and of the original melody. Like her contemporary Betty Carter, Jordan first fell in love with bebop–she was briefly married to pianist Duke Jordan, a sideman to Charlie Parker in the 50s–but has spent a lifetime pushing at, and beyond, its boundaries. She’s also spent most of her career performing only part-time, finally leaving the workforce in her 60s and finding an audience sufficient to support her; like Von Freeman, it took her five decades to become an overnight sensation. $10. Friday, May 28, 9 PM, and Saturday, May 29, 8 PM, Green Mill, 4802 N. Broadway; 773-878-5552.

Art accompanying story in printed newspaper (not available in this archive): photo/Michael Jackson.