Grand Junction Rockestra is practiced and ready for its first concert of 2013, and their seventh since the rock 'n' roll orchestra first took the stage in June 2011. Since its inception, GJR has performed classic rock 'n' roll with a twist; that twist being a live orchestra providing killer accompaniment to a talented rock band and vocalists. Somewhere between Katie Walters soulful and heartfelt singing of Whitney Houston's "I Will Always Love You" and Miss Emily's funky performance of Cee Lo's "Forget You," this writer realized that the twist might not only be the live orchestra but also the way a group performing classic rock n' roll can adapt so many different genres from several decades.How do you define classic rock? A quick reference check (meaning I searched in Wikipedia) states that the classic rock format features music ranging generally from the late 1960s to the late 1980s, primarily focusing on the hard rock genre that peaked in popularity in the 1970s. While I would tend to agree with this observation because I grew up in a household where music of the '60s and '70s was commonplace, you would probably get a different answer from someone who was a teenager in the 1950s and listened to greats like Chuck Berry and Elvis Presley.Or take a walk across the campus of Colorado Mesa University and talk to a handful of students (many of whom were born between 1992 and 1995, if you can believe it) and their answers to what classic rock is might cover some late '80s and even early '90s hits.Saturday's concert, which starts at 7:30 p.m., is the first-ever themed concert that Dr. Calvin Hofer has arranged with "hits from the '50s to the '90s." The 1950s will feature Chuck Berry's "Johnny Be Goode," Bobby Darin's "Mack The Knife," and Elvis classics "Jailhouse Rock" and "Love Me Tender." The latter will feature guest vocalist Kelly Anderson. Anderson is the executive director of the Grand Junction Symphony Orchestra and a leading operatic baritone, who performed last week with the Los Angeles Philharmonic.The 1960s will feature hits by The Beatles, The 5th Dimension, The Rolling Stones and Johnny Cash's "Ring of Fire," again performed by Anderson. Hits of the 70s include The Doobie Brothers, Lynyrd Skynyrd and Black Sabbath. Alabama, Toto and a Poison medley provide the backbone for a great '80s tribute and Santana's "Smooth," Bonnie Raitt's "Something To Talk About" and Nirvana's "Smells Like Teen Spirit" round out the 1990s.The entire set-list is available on the Grand Junction Symphony's website or you can become a fan of the Rockestra on Facebook and stay up to date with everything happening. Whether you subscribe to the notion that classic rock is late '60s to late '80s or you fall somewhere on either end, this concert will feature something for everyone. Generations X or Y might enjoy some Bobby Darin or early Rolling Stones and the baby boomers might find themselves tapping their feet to The Eagles or Toto's "Rosanna."Tickets for the concert are $20 and $25 and can be purchased online at gjsymphony.org, by calling 970-243-6787 or visiting the Symphony office at 225 N. Fifth St., suite 120. Beer and wine will be available before the concert and during intermission. Special thanks to Breckenridge Brewery and Grande River Vineyards for their continued support of the Grand Junction Rockestra.