Gretna Music will present concerts by Turtle Island Quartet on Sunday, July 21, at 7:30 p.m. and Apollo's Fire on Monday, July 22, at 7:30 p.m. Both events will take place at the Mt. Gretna Playhouse, 200 Pennsylvania Ave., Mount Gretna.

Founded in 1985, the Turtle Island Quartet strives to create new, bold trends in chamber music for strings. The group fuses the classical quartet style with a modern sound. The group consists of Gabe Terracciano and David Balakrishnan on violin, Benjamin von Gutzeit on viola, and Naseem Alatrash on cello.

In Mount Gretna, the quartet will perform several of Balakrishnan's compositions, including the three-movement work "Island Prayers," which is also the name of the program. The concert will also feature pieces by contemporary composers Rhiannon Giddens, Terence Blanchard, and Jerod Impichchaachaaha' Tate, who is a Chickasaw composer.

There is a ticket fee. Doors will open at 6:30 p.m., and pianist Sean Skinner will present a First Listen performance at 6:45 p.m. First Listen programs present local youths in free mini-concerts before the mainstage concerts.

Grammy-winning ensemble Apollo's Fire is led by award-winning harpsichordist and conductor Jeannette Sorrell. The period-instrument orchestra is dedicated to the Baroque concept of evoking emotions from the audience. The ensemble's current members include Alan Choo, violinist and concertmaster; Andrew Fouts, violinist and assistant concertmaster; and Emi Tanabe, principal violinist, along with Chiara Fasoli Stauffer on violin; Nicole Divall, viola; Rene Schiffer, cello; Tracy Rowell, contrabass; and William Simms, lutes and guitar.

The orchestra will present a program titled "Vivaldi's Four Seasons - Rediscovered." It will explore the famous four-movement work by Vivaldi, accompanied by the works of other Renaissance and Baroque composers. The program will also feature the soprano voices of Andrea Walker and Anna O'Connell, the latter of whom is also a harpist who performs Baroque music.

There is a ticket fee. Doors will open at 7 p.m. In addition, classical music promoter and influencer David Srebnik will give a free pre-concert lecture at 6:30 p.m. in the Hall of Philosophy, 212 Gettysburg Ave., Mount Gretna.

For tickets and more information, call 717-361-1508 or visit http://www.gretnamusic.org.