A jolly good time: Acclaimed Irish singers Maura O’Connell and Karan Casey grace The Kate

Contributed photos Irish singers Maura O’Connell and Karan Casey will have a jolly good time at The Kate.

OLD SAYBROOK >> Karan Casey has been dubbed the Irish equivalent of Emmylou Harris by the Washington Post. Maura O’Connell has a voice so true and powerful that, when the power went out during a concert, she walked out in front of the microphone and sang.

Together, Casey and O’Connell, among Ireland’s most beloved singers, will appear at The Kate on Saturday, Aug. 13, for an evening of songs and stories.

For now, the two, reached in Nashville, where Casey is bunking with O’Connell between performances in Washington, D.C. and Vancouver, seem to be having a jolly good time.

“We’re just rehearsing and hanging out,” said the County Cork resident, wife of Irish concertina player Niall Vallely, and mother of two, in a lively, wide-ranging conversation. “I’ve wanted to work with Maura for years.”

Not surprising, perhaps, given the burnished alto of the internationally acclaimed O’Connell, 58, as well as her jovial personality, “as big as her native County Clare,” according to music critic Michael Scott Cain. (For its part, the Los Angeles Times has called the voice of Casey, 47, “as pure and clear as the crystal from County Waterford, where she was born.”)

Not to mention O’Connell’s enduring mission to “bring back honor to the art of singing,” she said, one that, as Casey put it, “Maura has the vocal chops to have pulled off.” For O’Connell, a pure singer, (she doesn’t compose), singing is a simple joy, an elemental pleasure that didn’t require instrumental accompaniment.

“I’m always being asked why I don’t play an instrument to accompany myself, or why don’t I write songs,” she said. “It’s my belief that singing is a viable talent on its own.”

The aim, said the third of four singing daughters, with a mother who also sang, is to find the songs—“the good songs,” as she put it — that have “power, poetry, and tragedy in them.”

It’s a sensibility that began with her mother’s collection of light opera, opera, and parlor song records. Being exposed to those tunes, along with Celtic folk tunes, taught her that “singers don’t have to be tied to a particular style — country, pop, whatever. They shouldn’t be bound to anything but the song.”

It was a realization that ultimately prompted her 1986 move to Nashville and the experimental roots movement, where musicians were blasting away at genres and deliberately transcending all the established limits.

For her part, Casey took a different route to America, studying jazz at Long Island University beginning in 1993, singing in bars and clubs in Manhattan and, ironically, finding herself drawn back to Irish traditional music with the band Solas.

Each found success. Since launching a solo career in 1999, Casey has released six albums, winning praise from Hot Press as “a vocalist of the rarest quality” and from the New York Times for “setting her clear voice in arrangements that mix traditional and modern instruments.” She was a regular on “Prairie Home Companion” and also has made appearances at the Kennedy Center, the Grand Ole Opry, and with the Boston Pops.

O’Connell’s singing career has brought her two Grammy nominations, guest appearances on the albums of such luminaries as Rosanne Cash, Van Morrison, and Dolly Parton, as well as collaborations in her most recent release, the Grammy-nominated “Naked with Friends,” with the likes of Alison Krauss.

“The idea of doing ‘Naked With Friends,’” which consists of 13 unaccompanied tracks, “had been with me a very long time,” said O’Connell, who Martin Scorsese cast in his 2002 “The Gangs of New York” as an Irish migrant street singer. “I just wanted to capture the feeling of joy that comes from people singing together.”

She’s already realizing that with Casey, whose most recent release, “Two More Hours,” in contrast, has her breaking new ground. A departure from the traditional music for which she’s known and her first entirely self-penned album, it’s a highly personal collection of songs in memory of her mother who died in 2010.

“It’s about getting through things and getting through grief,” she said. “It’s about trying to get to the truth of myself.”

It’s also, according to music critic Carol Rifkin, a mix of “sweet vocals, new material, and Irish charm.”

Which, the two promise, will be on full display Saturday night. “Good songs,” they said in unison when asked what else was in store, before breaking out in laughter.

Maura O’Connell and Karan Casey will appear at the Katharine Hepburn Cultural Arts Center at 8 p.m. on Saturday, Aug. 13, 300 Main St., Old Saybrook. For tickets and information, visit www.katharinehepburntheater.org or call 877-503-1286.

Lisa Reisman’s award-winning memoir, “5 Months 10 Years 2 Hours” is available on amazon.com.