St. Isidore of Seville (d. 636) and Pope Gregory the Great (d. 604) had an intellectual exchange facilitated in part by Isidore’s brother Leander (d. ca. 600), who preceded Isidore as bishop of Seville, had met Gregory in Constantinople, and to whom Gregory dedicated his Moralia in Job. Isidore’s writings and contemporaneous records of Spanish church councils make clear that the Old Hispanic Rite was already largely, though not entirely, formed in his day, much as we find it in the earliest surviving liturgical documents: the Oracional Visigótico (ca. 711) and the Antiphoner of León (ca. 900). This is a rite deriving from a great exegetical project in which liturgical chant formed only a part. Its starting points were the various translations of the Bible and the writings of the church fathers, especially Gregory and Augustine. From this an elaborate and systematic repertory of chant was formed in coordination with prayers, readings, and sermons. All of this speaks to deliberate composition by Isidore, Leander, and their colleagues rather than to the writing down of a long-standing oral tradition. Gregory surely knew about this activity in Spain. Is it likely that Gregory and his colleagues were not engaged in any such activity or that such activity in Rome took place so much later than it did in Spain? Perhaps there is a good reason why the chant created in Rome is called Gregorian just as the Old Hispanic Chant was much later called Isidorean. In the absence of Roman sources we may never know. But the Old Hispanic sources suggest that we ought to wonder.

The motet Summus secretarius remains an enigma in the polyphonic output of the south Netherlandish composer Johannes Brassart (ca. 1400/5–1455). While extant sources (I-Bc Q15 and GB-Ob 213) attest to Brassart’s authorship, the message and function of this motet have long perplexed musicologists seeking to identify the work’s elusive subject and understand its cryptic language. Who is the “highest secretary” hailed at the outset, and what is this figure’s relationship to the biblical and cosmological references in the ensuing lines? Summus secretarius reveals its secrets when examined within the context of the medieval cult of St. John the Evangelist. Taking cues from Brassart’s careful musical treatment of words quoted from the Gospel of John (1:1), we can decipher the motet’s language and symbolism using a diverse array of exegetical writings, images, and liturgical music that illuminate the unique status of John as Christ’s most intimate confidant, the seer and evangelist privy to his secrets. Brassart would have experienced the evangelist’s cult most vividly through his service as singer, chaplain, priest, and canon at the collegiate church of Saint-Jean l’Evangéliste in Liège—the most likely place for the motet’s composition and performance. Summus secretarius demonstrates to an exceptional degree the hermeneutic richness of enigmatic language in the unique texts of freely composed fifteenth-century motets.