For the first time in Russian musicology, the article examines two motets by major Renaissance composers — William Byrd and Philippe de Monte. The history of their origin is non-trivial: the motets are a kind of letters that composers exchanged in 1583–1584. Without touching on the problem of a hidden political program, which Western researchers usually write about, the author examines the compositional features of each of the works. The two motets are united not only by a common textual basis, namely the verses of Psalm 136, but also by a common constructive idea—the technique of inversion, which Byrd borrows from Monte, “answering his letter.” In addition, the motets in manuscripts of that time are located one after another. The circumstances of the appearance of the two works and the commonality of compositional techniques speak in favour of the fact that these motets represent a single whole. From a historical perspec­tive, the phenomenon of Byrd’s and Monte’s motets raises the more general issue of exchanging musical letters between composers.