The orchestra, directed by former music director Keith Lockhart, will accompany singers and songwriters Emily Saliers and Amy Ray, and Saliers said she couldn't wait.
"We are so excited to do this," she said during a telephone interview with The Park Record. "This is something we started doing a little more than a year ago and it's been quite the experience when it comes to how we tour."
Usually, Saliers and Ray tour either as an acoustic duo or with a drummer, bassist and keyboardist.
"Playing with a symphony is a completely different experience, and we work with a separate agency for the symphony shows," Saliers said.
In order to get music to the different orchestras, the Indigo Girls hired music arrangers Stephen Barber and Sean O'Loughlin to arrange 18 to 19 songs, Saliers said.
Barber has worked with Rosanne Cash, Alejandro Escovedo and John Legend, and O'Loughlin has arranged works for Chris Isaak, Feist and The Decemberists.
"The scores are then sent to the different conductors and orchestras that we will perform with," Saliers said. "When we get to those towns, we have one rehearsal session that lasts 2 ½ hours and then we play the show."
Saliers and Ray chose 19 songs for symphony treatment.
"They range from rock songs to tender ballads," Saliers said. "Some are really stripped down and some have a lot of orchestration.
"It's quite exciting for us because each symphony and conductor is different," she said. "It's also a great experience for us, because is requires heavy focus and concentration on our part."
When the Indigo Girls were asked to select songs for these concerts, their management recommended some of the sing-alongs hits that Saliers said she might have not have chosen.
"We did pick 'Closer to Fine' and 'Power of Two,' because we were asked to pick those, but the other ones run the gamut," she said.
One is a rock-punk song by Ray called "Compromise" and another is one that Saliers wrote called "Ghost" that already has string arrangements on the original version.
"It was fun wondering what 'Compromise' would sound like," Saliers said. "I also have a song from our latest record, 'Beauty Queen Sister,' called 'Able to Sing,' and I have always wondered what that would sound like orchestrated."
The concert will also feature a song called "Damo," a piece with some Celtic influences that was written by Ray for Damien Dempsey, a singer in the United Kingdom.
"We really had fun picking songs and tried to imagine how they would turn out orchestrated," Saliers said.
Playing with a symphony is another step for the Indigo Girls' musical journey that began when they were kids.
"I grew up in a musical family and my grandfather was a touring musician in the big-band era," said Saliers, who sang in various choirs in her youth. "My mother was a professional dancer and my father studied classical and jazz piano, so performing came to me through the bloodline."
Ray's home was also filled with music, Saliers said.
"Her big sister played the guitar and Amy would listen to all her albums," she said.
Saliers met Ray in elementary school, and their paths converged throughout their education.
"We both attended the same college and when we graduated, we already had a fledgling career going," Saliers said. "We really didn't aspire to any sort of success. We just wanted to have fun and challenge ourselves and get the next best gig. And performing with a symphony is something that we would never have imagined."
Although the Indigo Girls are playing with full orchestras, their involvement in social activism hasn't changed since their early days as a bar band.
In the past, Ray and Saliers have worked with the Goshute Tribal members to prevent nuclear waste from being dumped on their reservation in Skull Valley, Utah. They also partnered with an organization called Honor the Earth to introduce solar power to the reservation.
The Indio Girls are currently working with the National Coalition to Abolish the Death Penalty.
"First and foremost, the death penalty is the ultimate punishment and, unless the system were perfect, which it never will be, there are so many opportunities to make mistakes when it comes to race and socio-economic class," Saliers said. "We're working with Georgians For the Alternative for the Death Penalty, and we're working to raise money for the Texas Moratorium on the death penalty. They just executed their 500th inmate since the death penalty was reinstated in 1976."
To raise money for the cause, the Indigo Girls will sell T-Shirts at the concert to raise money.
"I don't think it's important for an artist to do things like this, but I am thankful that they do, because music is such a galvanizing force for change and many artists have a certain amount of influence," Saliers said.
Activism started from a belief that the two women were taught by their families.
"We are citizens and it's important for us to take part in the world around us, starting with our community," she said. "We both have strong interest in social issues and causes and change. So, when we were starting out as a bar band, we found we could play a concert and raise money for a homeless shelter or raise awareness for groups that need assistance."
The Deer Valley Music Festival continues with The Indigo Girls and the Utah Symphony at Deer Valley's Snow Park Amphitheater on Saturday, July 20, at 7:30 p.m. Tickets range from $37 to $95 and are available by visiting www.deervalleymusicfestival.org.