Isaac just might be described as the 15th century’s answer to Telemann, his output vast and versatile but uneven. This is borne out in the discography, though fortunately the centrepiece of this new recording is a very fine Mass setting for six voices, based on one of Isaac’s most famous motets. The programme might be described as a semi staged liturgical reconstruction of a Mass sung in Florence in the presence of the Medici pope Leo X, whose family were among Isaac’s most steadfast patrons (though Missa Virgo prudentissima, which as far as I’m aware has never been recorded before, was most likely composed during Isaac’s stint at the Imperial court). As a consequence, the recording includes a good deal of plainsong.

The polyphony is well handled for the most part, especially in the early stages of the Mass and the excerpts from Isaac’s posthumous magnum opus, Choralis Constantinus. Rarely has this ensemble sounded so full and blooming in sacred polyphony, helped by the presence of two sopranos for the top line. In the Credo, however (try the opening section), there are signs of fatigue, and the loss of precision of detail affects the projection of large-scale structure. The delivery of the plainchant is more consistent, though some decisions concerning its interpretation puzzle me (particularly the style of the added voice in the Communion, a matter on which the programme note is silent). Despite these reservations, Isaac is at or very near the top of his game in this imposing programme, so aficionados of this period needn’t hesitate.