POP MUSIC REVIEW : PROPINQUITY PERKS UP WARWICK, MATHIS SHOW

There’s an added dividend for the audience when two artists who respect each other share a stage: They’re usually motivated to do their best work. This was certainly the case with Johnny Mathis and Dionne Warwick’s opening show Wednesday night at the Greek Theatre.

Warwick has long been one of our most gifted singers, but she’s tended to hold back in recent concert appearances, sometimes even sitting on a stool while singing a medley. There was no stool in sight Wednesday as Warwick tore through a stirring set that was startling in its intensity. Mathis, too, seemed to rise to the challenge--and the potential--of the double bill. His first set of light sambas and courtly ballads failed to match Warwick’s intensity, but he mustered more stamina for his second set, highlighted by a superb “West Side Story� medley.

It’s a bit unfair to compare Mathis and Warwick because they’re different types of singers, a fact dramatized by the choice of artists each saluted in their shows. Mathis noted that his “big hero� growing up was Nat (King) Cole, the master of classy, understated ballads. Warwick paid tribute to Mahalia Jackson with a rousing gospel piece.

Where Warwick used to rely on taped-duet gimmicks in her show, now she’s really putting out. On this night, she sang all the vocal parts on the recent Dionne & Friends smash “That’s What Friends Are For,� and even sang all the parts on last year’s “We Are the World,� in which she participated. The 44-year-old star also did justice to the chunky groove of “A Little Bit of Love� by the teen sensations, New Edition. My only reservation is that now and again the vocal fireworks seemed to be for their own sake, rather in service of the song.

Mathis’ set proved that he remains the king of the romantic ballad. His vocal tone and control are as fine as ever. He should, however, restructure his set, dropping the overly familiar pieces (“Brazil,� “Begin the Beguine�) and moving a few powerhouse pieces into the first half. The engagement runs through Saturday.