Cantus, with nine men, and Rose Ensemble, with a mixed ensemble of 12, demonstrate the joys to be found in smaller vocal ensembles. Their Christmas concerts, "Christmas With Cantus" and "Slavic Wonders," offer radically different, but equally satisfying holiday experiences.

Cantus' diverse program is the more immediately accessible, but Rose Ensemble's focus on centuries of music from Russia and Eastern Europe offers a striking musical experience.

There's something awe-inspiring about the way the men of Cantus seem to sing as one organism, watching each other, even breathing together, creating perfectly balanced harmonies. And they do it all with a warm, burnished tone.

From medieval carols to contemporary classical music to pop Christmas music, they proved themselves masters of all the diverse musical styles.

Rose Ensemble created a strong Russian sound, adding a stylistically appropriate rough burr to their tone. The basses shone with sounds that seemed to come from the center of the Earth, and the sopranos' crystalline sound was clear and pure to the top of the register.

From the austerity of traditional Ukrainian chant to traditional folk carols to a contemporary Russian chorus that Rose Ensemble had commissioned, the program was more diverse than I'd expected, sung with robust enthusiasm and the true spirit of the season.

A highlight of the Cantus program was the world premiere of "Cantate Domino" by ensemble member Paul J. Rudoi. The ensemble responded with a joyous enthusiasm in this almost pop setting of the Latin text.

A crowning moment for Rose Ensemble was a Magnificat by 17th-century composer Mikoaj Zielenski, written for 12 parts and in three antiphonal choirs, in the ornate Italianate style. They sang the intricate harmonies with stunning clarity.

Rose Ensemble provided a very simple staging, like processing in to an early Russian Orthodox chant, which effectively gave drama and theatricality to an admittedly heavy repertoire. They made the unfamiliar music both approachable and entertaining.

Occasionally, Cantus become so concerned with creating perfect harmonies that the result sounded overly studied. But when they let themselves cut loose, they had great fun, as with "Skating" by Vince Guaraldi, a jazz vocalise with some great scat singing. A calypso rendition of "We Wish You a Merry Christmas" brought the concert to a rousing conclusion.