Although the OC Fair ended Aug. 11, Pacific Symphony’s Wavelength Festival of Music has provided one more weekend of concerts, extending Pacific Amphitheatre’s summer schedule via four eclectic performances.

Night 1 played out Thursday with singer-guitarist Bonnie Raitt headlining a bill also featuring master bluesman Keb’ Mo’, the Barry Perkins Collective and violinist Josh Vietti.

+ 12

Raitt’s 110-minute main set was everything a fan of the Grammy winner could ask for and more. She was just as relaxed and engaging with fans as during her memorable headlining turn at the Doheny Blues Festival in May 2008, yet this Costa Mesa crowd seemed comprised mostly of diehards, as opposed to partying festival-goers who test the patience of music enthusiasts. The result was a chance to really hear Raitt and her top-notch four-man band perform potent versions of her staples as well as gems from her latest album, last year’s outstanding “Slipstream.”

Indeed, the reworked classics that fill that disc were among the highlights here. Her reggae-tinged take on Gerry Rafferty’s “Right Down the Line” found Raitt closing the song with an expressive and extended slide-guitar solo, layered artfully with riffs from fellow six-stringer George Marinelli. An acoustic blues ride through Bob Dylan’s “Million Miles” featured keyboardist Mike Finnigan and Marinelli in a consummate demonstration of how even quiet material can become charged in the right hands.

Later, the album’s strengths shined again via a commanding performance of the folk-rock tune “Marriage Made in Hollywood,” a beautiful piece penned by Paul Brady and Michael O’Keefe (Raitt’s ex-husband), given an irresistible arrangement featuring an acoustic breakdown and room for Marinelli to deliver two sharp, distinctive solos.

Raitt remains eager to please fans and of course offered up her best-known songs (“Something to Talk About,” her version of John Prine’s “Angel from Montgomery”) with forceful renditions throughout the night, and though now 63, Raitt’s glowing soprano remains a mighty force.

She launched her memorable encore with a hushed take on the heart-wrenching “I Can’t Make You Love Me,” her emotionally nuanced delivery quieting the crowd. The reggae-flavored “Have a Heart” reignited the upbeat mood en route to Keb’ Mo’ joining the headliner for a rousing handling of Aretha Franklin’s “Baby I Love You” and a final Chuck Berry-esque rocker that richly closed things out.

Keb’ Mo’ took the stage to plenty of cheers and over the course of 35 minutes used nothing more than a few acoustic guitars and a harmonica as he performed original material that quickly connected with people. While possessing a warm baritone voice, it’s the singer’s personable style and solid command of Delta blues and slide guitar, all layered onto real-world tales of love and loss, that really solidifies his work.

Songs such as “Government Cheese” might come off silly in the hands of many players, but Keb’ Mo’ brought that tune to vivid life with realistic details of poverty-stricken struggles. Likewise, his love song “Shave Yo Legs” brought plenty of laughter, yet at its core it’s a beautiful song that delves into deep and unconditional love in a winning performance.

Barry Perkins, principal trumpeter with Pacific Symphony for close to a decade, opened the main stage with his local collective, including fellow PSO members Elliott Moreau (saxophone), Robert Schumitzky (violin) and Laszlo Mezo (cello). They performed an instrumental set of classical, pop and Latin jazz for early attendees, standing out with the lovely “Cinema Paradiso” and an up-tempo version of Stevie Wonder’s “Overjoyed.”

Performing in the concourse outside the main amphitheater Thursday evening (and again Friday), violinist Josh Vietti showed off virtuoso chops on his instrument as people entered the venue. One fan in a cowboy hat was thrilled when the fiddler fulfilled his request to play the iconic solos from the Charlie Daniels Band’s signature song “The Devil Went Down to Georgia.”