Edward Wickham and the Clerks' Group have changed their tune (as it were) since beginning their Ockeghem series in 1994. In earlier recordings such as the Missa Mi-Mi and the Gramophone Award-winning Requiem, their sound was typical of the English style of early-music performance made world-famous by the Tallis Scholars: clear, smoothly blended voices and a reverent but somewhat reserved approach clearly indebted to Anglican church tradition. Five years on, they're using a throatier vocal tone and more energetic tempos. Whatever they're losing in meditative beauty, they're making up in vigor--Wickham's Ockeghem is definitely not the dusty old cerebralist heard in undergraduate music history courses. Alongside the three-voice Missa Quinti Toni and the low-pitched, possibly apocryphal motet Celeste Beneficium (in a marvelous one-voice-per-part performance), this disc presents the Missa Cuiusvis Toni ("Mass in whatever mode you wish"), one of the works that cemented Ockeghem's reputation as the Renaissance's musical puzzlemaster. ("Major" and "minor" are modern-day modes; Ockeghem designed this Mass so that it could be sung in different modes, depending on which note the singers start on.) ASV and the Clerks' Group give us the entire Mass in the Phrygian mode (a solemn-sounding scale with no modern equivalent) and, for contrast, the Kyrie and Agnus Dei in Mixolydian (similar to a major key). Now if only a brave choir and record label would record this Mass in all four of the main modes--it would fit (barely) on one CD, make a good illustration for music history students, and fascinate early-music buffs. --Matthew Westphal