A musical icon for more than 50 years, Diana Ross long ago reached an elite level of super-fame to the point where her songs are everywhere—even if they aren’t on the radio all the time. Her ascent to fame with The Supremes was chronicled in the thinly fictionalized Broadway musical Dreamgirls, with Beyoncé Knowles taking on the Ross part in the play’s 2006 film adaptation. That gives an indication of Ross’ bravado and prowess as a singer, but even Beyoncé would agree Ross is in a class of her own. With so much well-earned, storied history behind her, naturally Ross is all about looking back these days. Her current tour, titled “More Today Than Yesterday,” is advertised as a trip through the diva’s greatest hits.