Alternative-bluegrass singer Aoife O’Donovan teams with Heather Masse of the Wailin’ Jennys for a night of folk in the San Juan Community Theatre, Friday, 7:30 p.m.

The theater refers to the two as folk “goddesses,” but that description doesn’t really tell islanders what’s in store: O’Donovan’s warm, mesmerizing vocals. Masse’s voice, which Sing Out magazine wrote hovers “somewhere between Alison Krauss and Maura O’Connell.”

The two should be a strong combination in concert.

O’Donovan (her first name is pronounced “ee-fuh”) is arguably one of the busiest singers in her genre today, dividing her time between the alternative bluegrass quartet Crooked Still, the female trio Sometymes Why, and her solo career.

Crooked Still is referred to by The Boston Globe as “the most important folk group to emerge from Boston since the early ‘60s.”

O’Donovan says her music “sounds like” raspberry Heath bar frozen yogurt with homemade popcorn on the side. Perhaps. But she can make “mellow” smolder; you can feel the temperature rise when she and Crooked Still perform the mellow-bluesy “Come On In My Kitchen.” VIDEO .

Uptown Magazine in Winnipeg gave a vivid description of what islanders can expect when Masse’s at the mike: “(Her) surprisingly deep vocal sent a ripple of reaction through the audience. It’s a throaty voice, fit for sultry jazz, and it was best showcased on a spooky a cappella rendition of Lead Belly’s ‘Bring Me Little Water Sylvie.’ ”

Masse, a native of Maine, is now based in New York where she divides her time between performances with the Juno award-winning Wailin’ Jennys and her own projects. Masse is a regular guest on “Prairie Home Companion” and performed with O’Donovan with the contemporary bluegrass band “The Wayfaring Strangers.”

Masse’s voice has been described as elegant, rich and soulful, and “she moves through numerous styles organically and with sincerity, a quality learned from early influences as disparate as Ray Charles, Bonnie Raitt, Joni Mitchell and Chet Baker.”

Sing Out magazine wrote that Masse’s voice has the versatility “to take on material as widely diverse as Johnny Cash’s ‘I Still Miss Someone.’ Hank Williams’ ‘Weary Blues from Waitin’,’ Paul Seibels’s ‘Louise’ and old-time standards like ‘Train on the Island,’ yet give them each her own intriguing twist.”

Tip: If you miss the performance or want another dose, O’Donovan and Masse will perform Saturday, 9 p.m. in The Rockfish Grill in Anacortes.

— Tickets: $20 adults, $10 student reserved, $5 RUSH at the door. Call 378-3210 or visit www.sjctheatre.org.