This disc, by an English ensemble specializing in Continental sacred music of the Renaissance, would seem to be aimed at specialists with its mysterious subtitle of "The Alternatim Practice at the Imperial Court" and its highly detailed examination of the music recorded. And so it is. Yet, as with the unexpected foreground image of two dogs playing in the inside-front-cover woodcut of Kaiser Maximilian celebrating Mass, there's a good deal here to interest the general listener. To condense the notes to a point probably beyond what is acceptable, the disc explores an unusual way of setting the text of the mass: "alternatim" settings, found in various countries, set phrases of the text polyphonically while leaving others to be sung as chant, for an antiphonal effect. The new wrinkle in Heinrich Isaac's Austria was that the chant sections might be replaced by organ improvisations on the chant melodies appropriate for the day's service. Subsidiary themes of the album include the persistence of tropes or additions in the mass texts of this period, and the tendency of composers of this epoch to rework, likely at the Kaiser's request, finished pieces of their own or others.
The music on the disc illustrates these rather arcane phenomena clearly, and it's smoothly and expressively performed by the sextet Ensemble Hofkapelle. The program opens with a chant, followed by an organ piece based on it by the leading keyboard player of the time, Paul Hofhaimer (1459-1537). Then come two Isaac mass settings based on chant cantus firmi, a four-voice Missa de Beata Mariae Virgine and then its six-voice expansion. Neither mass has a Credo section, for reasons that the booklet delves into. The four-voice mass is performed alternatim with appropriate chants, while in the six-voice mass the chants are replaced with organ improvisations by David Blunden, performing on a 1457 Netherlandish instrument. The Gloria sections of the masses contain troped texts. Finally there is an expansion of Josquin Desprez's famed Ave Maria...virgo serena to six voices, perhaps by Austrian composer Ludwig Daser -- it's odd to hear the perfect transparency of that work muddied by additional voices, but the inclusion of the piece helps the listener understand Isaac's compositional world, which is still among the most mysterious for the modern listener of those of all classical composers. The Renaissance mass, in general, was never heard as today's listeners hear it, straight through. For the student or Renaissance sacred music enthusiast, this disc offers an interesting tour through one of the many forms of performance of the mass by a choir in a Renaissance chapel might take. The beautiful cover reproduction of Albrecht Dürer's portrait of Maximilian is almost worth the album's price in itself.