The old adage “the show must go on” came to mind Saturday evening when one member of the vocal quartet Anonymous 4 was hospitalized not long before the 5 p.m. Early Music Now concert at St. Joseph Center Chapel. If the remaining three members were agitated by circumstances (and who wouldn’t be?), it was not apparent. One had to admire their professionalism. Admiration did not end there.

The ensemble’s unique magic was undiminished in a program of primarily medieval carols in Latin and Middle English. Many of their custom arrangements are three-part to begin with, but surely the situation required musical adjustments. I kept listening for a missing fourth part; its absence was amazingly inconspicuous.

Anonymous 4’s most perfect blend and balance of any vocal ensemble is its calling card, along with unerring taste and creative programming. Easy fluency with varying styles is another strength. In solos the voices of Marsha Genensky, Susan Hellauer and Jacqueline Horner-Kwiatek had individual color that disappeared when singing together.

The medieval sounds were spelled with lively and refined arrangements of American folk carols, some of the most memorable selections on the concert. The singers sang with charming style that grew organically from bluegrass roots, more evidence of why Anonymous 4 has sold 1.5 million recordings over its long career.

Earlier in the week Prometheus Trio presented a rich concert at Wisconsin Conservatory of Music, including the rarely encountered Trio in C Major (“Lovisa”) by Jean Sibelius and Trio 1, Op. 3 by Alan Hovhaness. Both are early works, full of fresh energy and, as is the case with the best young composers, unconventional takes on convention. Sibelius, known for his symphonies, wrote relatively little chamber music, which makes this early trio even more interesting. Though not profound, its haunting folk-like melodies are signature for this composer. Hovhaness’ compact trio is a better piece, combining neo-Baroque with folk-inspired harmony. Though there were occasional tuning concerns, the Prometheus players gave illustrative, enlightened readings of these and two additional works, Mozart’s Trio in E Major, K. 542, and Schumann’s Trio No. 3 in G Minor, Op. 110.