It's interesting -- make that questionable -- how some reviewers have noted that Atlanta's Indigo Girls rock the house without the aid of testosterone.

 As if the hormone exclusive to men is a prerequisite to lighting up the spot.

 I suspect the Indigo Girls don't care for such nonsense.

 Neither do they have any interest in proving that women can rock out too.

 If you happen to be one of those sorry guys who still clings to the belief that a female rocker can't match the intensity of your fave male artist, you would be nursing a hole in your chest after the first five minutes of the Indigos' concert at the Molson Amphitheatre last night.

 That's the effect that show opener Go boasts. The anthem-like, hard-rocking jam that also happens to open last year's Come On Now Social was nothing short of a sonic boom.

 Go also contains these lines: "I know you kids can stand the rain, I know the kids are still upsetters, 'Cause rock is cool but the struggle is better, Go, go, go."

 Unlike the majority of their contemporaries, Amy Ray and Emily Saliers aren't scared to voice their views in their music.

 They've performed in support of pirate radio stations and Native American environmental groups, and list several political organizations worth helping in the booklet accompanying the Come On Now Social disc.

 And well before the renewed debate surrounding the effectiveness of the death penalty in the U.S., Ray penned Faye Tucker, a poignant song about the first woman executed by Texas since the Civil War. The song also happened to be one of several highlights of their memorable show here.

 It's impressive how many flavours their material boasts: There's the punk feel of Compromise, the gorgeous ballads Ozilline and Peace Tonight, and their sweet acoustic hit Closer To Fine, which had everyone standing and singing along, and others with a Celtic or folk vibe.

 All were delivered with superb harmonies, style and grace.

JAM! Rating: 4 out of 5