The Grammy Award-winner gave fans a taste of new material in the 14-song, 70-minute concert Friday at the Eau Claire Regional Arts Center in Eau Claire, Wis., People magazine reported Saturday.
"I'm totally cool and so happy; I think I'm about to cry," Rimes told fans while on stage. "Thanks for being awesome fans -- patient and understanding."
The new songs brought an edginess to Rimes' music that wasn't there before, People said.
"I'm pissed off at a lot of things, and I just can't say it," Rimes said on stage. "So, it comes out in the music."
Rimes was given permission from her treatment facility to perform a handful of previously scheduled concerts. She will return when those obligations have been completed.
Her first public appearance since leaving treatment was Thursday night at the MTV Video Music Awards at the Staples Center in Los Angeles.
Her publicist announced her voluntary admittance to the 30-day in-patient treatment facility Aug. 29.
"While there will be speculation regarding her treatment, she is simply there to learn and develop coping mechanisms," her representative, Marcel Pariseau, told People last month.