FLORENCE - A guy in the fifth row screamed out "Don't change a thing" to Tucson bluegrass band Run Boy Run.

It was perhaps the biggest compliment you could get from the crowd of several thousand as Country Thunder settled into Day 2 on Friday afternoon.

RBR opened the day's lineup, replacing Nashville trio Eden's Edge, which pulled out after lead singer Hannah Blaylock departed a couple of weeks ago.

Run Boy Run was the only band on Friday's lineup proudly billed as bluegrass, the noble forefather of country. The quintet - siblings Matt and Grace Rolland, sisters Bekah and Jen Sandoval, and Jesse Allen - performed what will likely go down as the most musical show of the four-day festival. Their instrumental arsenal included twin fiddles, stand-up bass, mandolin, guitar and cello, and several of them double-dipped on more than one instrument.

And boy, could they play the dickens out of them. On "Little Girl," award-winning fiddler Matt Rolland kicked off the soaring intro after the Sandovals and Grace Rolland soared on the three-part a cappella vocal harmonies. Bekah Sandoval followed Rolland's lead, and one by one each member chimed in, all at different tempos until the music built to a glorious swell.

The quintet warmed the stage nicely for Nashville rising star Greg Bates and veteran crooner Tracy Lawrence. Perhaps the most surprising hit of the day was emerging singer-songwriter Jana Kramer, who strutted onstage wearing impossibly high heels, leather shorts and enough sass with class to get all the wayward, whistling cowboys in line.

By the end of her hourlong set, Kramer, whose country-rocker fiance, Brantley Gilbert, headlined Country Thunder Thursday night, shucked the shoes and went barefoot. Then she launched into singing the get-back-at-the-boyfriend snarky ode "Walk All Over" as she strutted down the catwalk in a sea of outstretched hands from male fans and sang a new self-penned, spirited romp that set out the rules for dating her.

On StarNet: See more photos from Country Thunder at azstarnet.com/gallery


20th annual Country Thunder Festival at Canyon Moon Ranch in Florence. The festival continues through Sunday. Follow the live blog at live.azstarnet.com and join the conversation on Instagram, Twitter or Facebook with #AZThunder.

Contact Cathalena E. Burch at cburch@azstarnet.com or 573-4642. See www.azstarnet.com/calientetunedin for a review of Eric Church's headlining concert on Friday.