The 21st season of the Mainly Mozart Festival, taking place June 6-20, will offer some works by Mozart, but, this year, audiences will experience a lot more music by Tchaikovsky. True, it’s a Mozart festival, but variety is the spice of life, and, just as the work of Strauss was explored last year, who better than Peter Ilyich Tchaikovsky this year? Thirteen Tchaikovsky compositions, including three of his ballets — The Nutcracker, Sleeping Beauty, and Swan Lake — will be played by a stellar group of nationally recognized musicians. All performances will be in the beautifully restored Balboa Theatre in downtown San Diego. There is a wade range of ticket prices, and the top-level prices have been reduced in recognition of current economic challenges. Mainly Mozart has a proven track record of providing fine quality classical music. (619/239-0100, www.mainly mozart.org)   DARLENE G. DAVIES