When the Music Exchange came into existence some 10 years ago, it bore no resemblance to the all-female pop chorus group that exists today. For starters, there were males. But after a series of scheduling problems with most of the men in the group, the chorus went strictly X-chromosome. However, the biggest difference between now and then may be what the group’s performances accomplish.

Originally, the pop chorus sang exclusively at assisted-living facilities, hoping to bring some joy to the elderly. That was, until eight years ago, when a member of the group began to suffer from dystonia, a disorder that causes sustained muscle contractions and abnormal postures. “We held a benefit concert to raise awareness for dystonia, because most of us didn’t even know what it was,” said Lillian Goulet, Music Exchange’s director.

“Soon after that show, other organizations started approaching us to do benefit concerts for different diseases, and we’ve done a bunch since.” This Sunday the 25-member chorus, which typically specializes in pop numbers from the 1950s and 1960s, will host a holiday concert at the First Baptist Church in Nashua. The concert is free, but donations will be accepted to help support the group that supports so many others throughout the year.

“We know there’s lots of people who can’t afford to see Christmas concerts, but want to attend. We want to give them that chance,” Goulet said. The concert will feature two parts. The first is a series of older religious songs, and the second featuries a host of more familiar Christmas tunes, all done in the doo-wop styles of the Motown era. “It’s a great time to leave your stress behind and just enjoy yourself for a couple of hours,” Goulet said.