The Chandler Symphony Orchestra is a wonderful way to spend the evening! All of their concerts are free, which is great, and they perform at the Chandler Center for the Arts so it's a great venue too. I've been attending their concerts since I moved back to the Valley about three years ago and they are just wonderful. The musicians are excellent and the concerts are very well planned out.
A great option when attending a Chandler Symphony Orchestra concert is to get lunch or dinner (depending on when the concert is) in Downtown Chandler first then walk over to the Chandler Center for the Arts for the performance.
Their pops concert is always fun with special guest artists and exciting, fast-paced music that everyone knows and loves.
If you are looking for a wonderful and special evening activity, I highly recommend the Chandler Symphony Orchestra!