About this work
The collection this cantus firmus motet was apparently composed for Cantiones Sacrae (1575), which was a joint music-publishing venture by Byrd and Thomas Tallis. In publishing alongside Tallis, the young Byrd was apparently restless to ensure that his own music not be eclipsed by the elder master's. Byrd's contributions to Cantiones Sacrae are full of choices obviously made out of friendly competition. Miserere mihi, Domine is a double-canon piece that appears in Cantiones alongside a gigantic canonic work by Tallis. Since Byrd could hardly have competed in scale with Tallis' long piece, he chose instead to prove himself by using a formidably troublesome plainchant as his cantus firmus. The Miserere mihi chant, a terribly short melody with little intervalic content of interest, was a rather overused one by this point. Besides the difficulty of using it at all Byrd had the additional challenge of reviving stale material.
The "Miserere" only appears twice, once in long notes and then ornamented in a canon between the soprano and alto. Since there's only one upward leap in the entire chant, which mostly moves in steps, often downwards, Byrd has to milk that leap, a minor third, as much as possible. He makes that fragment the only one that is imitated in all the voices when the cantus firmus is stated. He manages elsewhere to entirely overcome the limitations simply by overlapping the best two motives he could draw from the chant with one of his own. A descending scale, we know, can be a marvelously pretty figure, and it is used as such here, along with the said rising third and his own lovely motive on "orationem meam." Placing the long-note version of the chant in the bass is shrewd too; it drives the piece with a tremendous, grounded push, and its very downwardness makes the top line sound all the more brilliant. And of course it's in the top line that that rising third is highlighted. Byrd's piece sparkles beside Tallis'.