Shannon Lambert-Ryan met her future husband and her future band mate at the Philadelphia Folk Festival.

Best of all, they were the same person.

Singer Lambert-Ryan, who grew up in the Philadelphia area, had long enjoyed the yearly festival, attending with her family as a child and later volunteering.

In 2006, she went there as a performer, singing with the Guy Mendilow Band, a Boston-based world music ensemble.

Fionan de Barra, a native of Dublin, Ireland, also was at the festival, performing with another band.

Lambert-Ryan and de Barra, a guitarist, met backstage and immediately hit it off.

"We weren't romantically interested in each other at the time," Lambert-Ryan says during a telephone interview, "but we were really just enamored by each other and spent the day walking around together and enjoying each other's company and said, 'Hey, it would be great to work on a project together.' "

A year and a half later, Lambert traveled to Ireland to work with de Barra on a collection of Irish and Scottish songs that she planned as her first solo album.

The album became the foundation for Runa, the Celtic band she and de Barra formed in 2008. Runa will perform Sunday night at Long's Park as part of the Summer Concert Series.

Lambert-Ryan and de Barra, who were married a short time after those Irish recording sessions, returned to Philadelphia and enlisted percussionist Cheryl Prashker as a full-time member of the band. Runa played its first gig in August 2008.

"Ever since then, the three of us have been the core group that has seen everything through," says Lambert-Ryan, who also is a step dancer, a talent she works into the band's show. "We've been at kind of a steady pace, going up the hill."

The band also includes multi-instrumentalist David Curley, a native of Galway, Ireland, who joined about two years ago and plays guitar, banjo, mandolin and bodhran. Curley also is a step dancer.

The newest member of Runa is fiddler Maggie Estes, a native of Louisville, Ky., who joined earlier this year and is a graduate of Belmont College in Nashville, Tenn., where she studied classical violin....