It's been said that music transcends language. The 18-year relationship between the Palo Alto-based Aurora Singers and French choir Chorale Assou-Lézert proves this to be true. On top of singing together at various exchanges, the two groups have bonded over life's ups and downs and fostered true international friendship.

This month, the Aurora Singers are hosting a local choral exchange with Chorale Assou-Lézert, marking their third joint program in the Bay Area. The exchanges -- which last about 10 days and involve social activities, cultural sight-seeing, performances and home hosting -- have been going on since 2001. The two groups will put on a free joint concert, "Together En Chansons," on July 21 at the Valley Presbyterian Church in Portola Valley.

Chorale Assou-Lézert first came to California and performed with the Aurora Singers in 2001, and once again in 2005, according to Aurora Singers Musical Director Dawn Reyen. Meanwhile, the Aurora Singers have visited Albi, France (one of Palo Alto's sister cities), in 2002, 2007 and 2016.

"Each time, we sang concerts together at least once, and have always sung impromptu songs when we have come across inspiring spots," Reyen said.

At the concerts, the Aurora Singers typically perform first, followed by Chorale Assou-Lézert. The third and final act consists of a joint performance with six songs: three in English and three in French.

Despite the cultural differences, Aurora Singers President Cynthia Mahood Levin said that both groups have similar styles, concentrating on popular music as the basis of their repertoire. However, she noted that because both groups also utilize different techniques, they are able to learn from each other musically.

"We have adored singing the timeless French songs, including those popularized by Edith Piaf and Jacques Brel," Levin said. "The French have a way with love songs that we try to emulate, but they're so much better at it."

Levin said that one of the best parts of the exchanges is that both groups are also able to embrace each other's cultures.

"The French have panache, and it is rubbing off on us in our costuming," she said. "It's not just in their flair with apparel. It's in their style of cooking and entertaining, always done with aplomb. At the same time, they've discovered the American potluck."

Nadine Cousinié, a member of Chorale Assou-Lézert since 2005, said her group usually sings popular French songs from the 1950s-1980s. Recently, she said the group has been experimenting more with gospel songs, a genre that they were introduced to by the Aurora Singers.

According to Philippe Ricca, a member of Chorale Assou-Lézert since 2014, through performing with the Aurora Singers, many of their members have also learned to be more present on the stage.

"In the past, we would just sing and our bodies were still," Ricca said. "From practicing with the Aurora Singers, we have started to act while singing, using our bodies and hands."

Ricca participated in an exchange in 2016, when the Aurora Singers flew to France. However, this exchange marks his first time in the U.S.

"I really enjoyed hosting them in 2016, singing the songs and coming together as friends," Ricca said. "I'm looking forward to singing together as usual. It's also my first time coming to the U.S. so visiting California and learning more about the culture here and how it is different from France."

Reyen said that although her favorite part of this exchange is singing together, she also appreciates the friendship that has formed.

"I've learned that we are really very much alike, and that singing together forms a special bond," Reyen said. "What a treat it is to come together in singing well-known French songs with native speakers, and how lovely to have them singing old American songs with us. I also love that we stay in each other's homes, and share in family life."

What: "Together En Chansons," with the Aurora Singers and Chorale Assou-Lézert.

Where: Valley Presbyterian Church, 945 Portola Road, Portola Valley.

When: Sunday, July 21, 4 p.m.

Cost: Free; donations accepted.

Info: Eventbrite.