Liedertafel is a four-man Oxford singing group I last heard a year ago in Wadham College Chapel, performing with the countertenor James Bowman. They were again first-class in a candlelit Christmas concert in Trinity College chapel last week.

As usual, their moving spirit Duncan Saunderson, a bass in New College Choir, was joined by Stephen Burrows (countertenor) and Ben Alden (bass), both in the Choir of St George's Chapel, Windsor, and this time by the tenor Matthew Vine, well known from his work with The Sixteen and his own vocal group, Vinum Bonum. As expected, their main repertoire was Renaissance polyphony, whose three- and four-part music always sounds so beautiful with a single (good) voice to a part; an unexpected and delightful bonus, however, was a series of readings by Colin Dexter - a long-term fan, it turns out, ever since Duncan Saunderson first started chatting to him about Morse's musical tastes.

These singers, all soloists in their own right, make a sound as far as possible from the fuzzily 'ecclesiastical' effect still associated with church choirs. I was going to say that they were at their best the more complex the music became, especially in such a masterpiece as the "Gloria" from the recently-discovered Missa Ave Regina Celorum of Jacob Obrecht (d.1505), a gem of Franco-Flemish polyphony. But that would be to underestimate the straightforward joys of good diction and perfect intonation in carols such as the 15th-century German Joseph Dearest, Joseph Mine and particularly Bach's exquisite arrangement of In Dulci Jubilo, the most subtle harmonic treatment possible of a simple tune.

I discovered, in talking to him later, that Saunderson has launched with the Liedertafel several of his own vocal arrangements of 19th-century piano music, including Schubert; this time we heard some 20th-century contributions to this lost art, largely based on pieces by Poulenc - particularly successful was Ding Dong Ding!, with the bells ringing in a distinctly French accent.