The birth of a genre surely is one of the most fascinating occurrences in the history of music, and no genre of medieval music had a more interesting birth than the motet. Study of the motet in modern times found special impetus and direction in 1898 when Wilhelm Meyer announced his discovery of the origin of the motet in the discant clausulae of the Notre Dame organa. Demonstrating the musical identity of certain Latin motets and discant clausulae, he concluded that the motet arose through the addition of Latin texts to the melismatic upper voices of the two-voice clausulae and was thereby able to explain for the first time the previously baffling and unprecedented verse structures of many motet texts. In doing so, he at the same time made it clear that he understood the French motet to be of later origin than the Latin and brushed aside special questions concerning the French type, such as, for example, its most provocative feature: its characteristic use of refrains. How was one to understand the presence of refrains in a French motet supposedly derived from a sacred, liturgical model? This and other difficult questions refused to disappear, and they continued to be raised from time to time, but Meyer's explanation of the origin of the motet gained general acceptance, most decisively and influentially from Friedrich Ludwig. All of Ludwig's writings on the motet bespeak his endorsement of Meyer's position, but nowhere more explicitly than in the Repertorium:

Of all the genres of thirteenth-century vernacular polyphony, none is more elusive than the so-called refrain cento. Such types of composition as the motet enté and the motet with a single terminal refrain make regular appearances in the literature on the thirteenth-century motet. Most of these genres are defined by the presence or absence of a refrain, the musico-poetic entity which seems to drift from chanson to rondeau, to verse narrative, to motet. The nature of the problem concerns the degree to which the pieces which have been termed refrain cento can actually be seen to constitute a genre. Generic considerations will therefore be given some weight in this article.

Antoine Busnoys's Missa L'Homme armé must have been one of the most highly esteemed polyphonic Mass cycles of its time. It survives in no fewer than seven sources, an exceptionally large number not equalled by any other cycle from the 1460s or 1470s – even those by Dufay and Ockeghem. In this respect Busnoys's Mass stands alongside a work such as the anonymous English Missa Caput, whose widespread popularity in the fifteenth century is also well established. It is a measure of their extraordinary esteem that both Masses served as models for ‘imitations’ by later composers. The entire cantus firmus layout of the Caput Mass was copied in Ockeghem's and Obrecht's cycles on the same tune, and possibly in a fourth Caput cycle of which only the Agnus dei survives. Busnoys's Missa L'Homme armé likewise served as the model for a later work, Obrecht's L'Homme armé Mass. There exists however a second ‘imitation’ of Busnoys's cycle, an anonymous Missa de Sancto Johanne Baptista, which probably dates from the 1480s or 1490s. This Mass has a less conspicuous relationship with its model than the other ‘imitations’ mentioned here, but it raises as many important questions concerning Renaissance practices of borrowing and structural modelling.

The front cover of Cod. 17561a in the Österreichische Nationalbibliothek, Vienna, bears the following inscription: ‘Dieses vollständige Requiem, bestehend aus Bl. 1–64, wurde im Jahre 1838 angekauft’ (‘This complete Requiem, consisting of ff. 1–64, was acquired in 1838’). Similarly, on Cod. 17561b we read: ‘Dieses unvollständige Requiem ist aus zwei Bruchstücken zusammengesetzt: (1) Bl. 65–86 (alt 11–32) wurden vom Abbé Stadler gekauft. (2) Bl. 87–99 (alt 33–45) wurden vom Hof-Kapellmeister Eybler geschenkt’ (‘This incomplete Requiem is assembled from two fragments: (1) ff. 65–86 (olim 11–32) were bought from Abbé Stadler. (2) ff. 87–99 (olim 33–45) were presented by Hof-Kapellmeister Eybler‘).