The comeback Cherry Tree Carol tour will land in the splendid chapel of the St. Joseph Center at 5 p.m. Saturday (Dec. , courtesy of Early Music Now. That's fitting, since Early Music Now first brought the quartet to Milwaukee in 1991, before the world had really taken notice. That was just before the release of their first unlikely hit CD, An English Ladymass, a reconstruction of a medieval British liturgy. That disc made them stars of the early music movement and a sellout international attraction.

In 1991, they sang for an audience of about 50 at St. James' Church on Wisconsin Avenue. Saturday, Ruth Cunningham, Marsha Genensky, Susan Hellauer and Jacquelin Horner-Kwiatek will sing for a sold-out house of 600.

"That was our first serious tour," Hellauer said, from Chicago, of the 1991 Milwaukee debut. "We love Milwaukee. It's been very important for us."

Early Music Now brought them back often, with an On Yoolis Night Christmas program at the Basilica of St. Josaphat being especially memorable. On in 2004 did they come to Milwaukee under other sponsorship; Artist Series at the Pabst bagged the farewell tour.

Hellauer said that the semi-retirement in 2004 occurred because all four women wanted to work on their own projects and because one member wanted to live in California rather than New York. Also, Anonymous 4 can't simply buy music off the shelf and sing a concert. They research, transcribe and arrange their music. The process requires library work, skill at reading old notations and getting comfortable with old versions of assorted languages.

"We decided to stop developing concerts," Hellauer said, explaining that they were willing to pull out an old one and work it up under the right circumstances.

They turned out to be victims of their own success. Great offers kept coming up.

"Who's gonna say no to the Edinburgh Festival?" Hellauer asked, rhetorically, of the opportunity that got them to travel once again, in 2007. And then there was American Angels, the album that had been in the pipeline for record label, Harmonia Mundi. This CD of American Southern songs, many in primitive three-part harmonies common in rural hymnals c. 1800, was a big departure for a group known for medieval European music. No one expected much from it. American Angels turned out to be the biggest A4 hit ever.

"We had No. 3 and No. 2 on the charts, but this was our first No. 1," Hellauer said.

The album opened a whole new audience and a new batch of presenters. Tour opportunities were too good to pass up.

The push behind the American repertoire came from Genensky, Hellauer said.

"Marsha went down to Arkansas and spent time with Almeda Riddle, whose knowledge of American southern folk and church music was encyclopedic," Hellauer said. "That music was Marsha's first love. She has that back-porch, high-lonesome sound."

Genensky will apply that sound to The Cherry Tree Carol, her solo on this program. That carol, which relates how a disgruntled Joseph discovers that God, not a competing lover, is responsible for Mary's condition. It dates at least to 15th century England. The program draws lines between old English Christmas songs and their American descendents.

Among those descendents were the "fuguing songs," canons, really, of William Billings and the shape-note books itinerant music teachers sold to backwoods American churches for decades. It was intended to be simple to learn and sing, and it is. The shape-note music is loaded with pedal tones and open fourths and fifths. It has at least that in common with early European medieval organum. But nothing about it is sophisticated.

"It's simple, but I wouldn't call it dumbed down," Hellauer said. "We sing it, we don't parody it. And then we have to think about how we sing. We can't scream and shout, as they might have done in a Southern church; that's just not who we are. Which brings into questions of style and authenticity.

"We always spend time in the library doing all this research and reading this treatise and that one. And then we have to do something that is true and honest for us and communicates with our audience."