Glen Campbell (search) called it "a captive audience" — and he wasn't kidding. Campbell, nearing the end of his 10-day sentence for extreme drunken driving, gave a free 30-minute concert Friday night for about 1,000 inmates at Maricopa County's outdoor jail.

"Tent City, you're gentle on my mind," Campbell sang during his opening song, the million-selling "Gentle on My Mind."

The Phoenix-based singer-guitarist performed several of his Top-10 hits on a makeshift stage atop a flatbed truck with some hay bales as a countrified backdrop.

Campbell, 68, was arrested in November near his posh Phoenix home after causing a minor traffic accident.

He pleaded guilty in May to extreme DUI (search) and leaving the scene of an accident, then began his jail term on July 1 with his final eight days set up as work-release.

Campbell was allowed to leave the jail, where he had a indoor private cell, during the day to handle business affairs, returning overnight.

"It's been an eye-opener, that's for sure," Campbell said of his time behind bars.

The country star also performed "By the Time I Get to Phoenix" in his eight-song set and led the rough-and-tumble audience in the chorus of "Rhinestone Cowboy (search)."

He even offered a little encouragement to the inmates, saying: "Sometimes it's hard to take what you get."