A holiday experiment by Anonymous 4

It was hard to say who was being put to the test more at UCLA’s Schoenberg Hall on Saturday night -- Anonymous 4, or their fans.

Rather than remain on their comfortable, usually soothing Middle Ages turf, the four female singers leaped forward several centuries -- yes, even into the 20th and 21st -- in a Christmas program titled “Wolcum Yule.”

Clearly a lot of thought went into the carefully conceived, symmetrical organization of material. Expertly accompanied by Alyssa Reit on a small Celtic harp on most numbers, the Anons divided the first half into four sequences in which each collection of traditional carols from the British Isles was topped off by a contemporary composition.

Within the sequences were subdivisions -- harp interludes, solo features for each singer -- and recurring subjects (parts of the Scottish poem “Balulalow” were heard in no less than three settings throughout the evening). Of the newer material, the most startling departure from the Anonymous norm was Peter Maxwell Davies’ “A Calendar of Kings,” full of jarring, clashing harmonies and a haunted tone that set off some murmuring in the audience afterward.

Ultimately, the most lasting impression of the program was left by the endlessly inventive Benjamin Britten, whose exquisite “A New Year Carol” ended the first half and provided a foretaste of “A Ceremony of Carols” -- itself based upon medieval texts -- after intermission.

Though Britten wrote “Ceremony” with a boys’ choir in mind, Anonymous 4 offered a less-innocent-sounding yet viable alternative, with sometimes swiftly paced, surprisingly impassioned results.