Tribute albums bring out the best and the worst in their participants. The most successful contributors pay homage while remaining true to themselves. Others try so desperately for dramatic interpretations that they wind up doing the celebrated artist a disservice. Cline would be smiling at the classy tributes paid by Norah Jones, Diana Krall, k.d. lang and Michelle Branch, but she’d be downright horrified by the florid, brassy efforts of Lee Ann Womack, Terri Clark and Martina McBride, who commits acapella sin with Take 6.