No-one has ever seriously questioned the exclusively monophonic character of medieval Byzantine ecclesiastical chant. The introduction of the drone, or ison singing, so familiar in contemporary Greek, Arabic, Romanian and Bulgarian practice, is not documented before the sixteenth century, when modal obscurity, resulting from complex and ambiguous chromatic alterations which appeared probably after the assimilation of Ottoman and other Eastern musical traditions, required the application of a tonic, or home-note, to mark the underlying tonal course of the melody. Musicians in Constantinople and on Mount Athos were probably oblivious of the rise of polyphony in the West, particularly after the formal break between the two Churches in the eleventh century, which was preceded by a long period of increasing estrangement. And with the Latin occupation of a part of the Byzantine Empire between 1204 and 1261, there was a general distaste for and rejection of the culture of the ‘Franks’.

The existence of an unsuspected and valuable set of Anglican Services and anthems first became generally known when they were catalogued at Sotheby's London Salerooms in 1969. It may seem remarkable that a major source of pre-Restoration church music should have escaped the puplic gaze for some 350 years: it is perhaps just as surprising that so rich a repertory should have originated from Chirk Castle, a remote spot close to the Welsh border in the county of Clwyd (formerly Denbighsihire).

In 1957 Nino Pirrotta expressed his view of Palestrina's music and the Tridentine reforms as follows:

The composers were directed to avoid too open an intrusion of secular elements, and to preserve the comprehensibility of the text so far as possible. That the latter would have been attainable through the avoidance of canons and other developed contrapuntal procedures (Animuccia, preface to Laude, Libro ii, 1570) is only in part true, if the noteworthy complexity of Palestrina's polyphonic composition is taken into account. In fact the problem had to be solved more from the spiritual than from the purely technical side. The true contribution of Palestrina and some of his contemporaries (e.g. de Kerle and Animuccia) to its solution — dramatised in anecdotes which do not withstand historical criticism — consists in the deep and inner religiosity which his works unquestionably express. This religiosity, joined to the responsibility for interpreting the official attitude of the Church, influenced the style in that it led to extreme circumspection in taking up the new means of emphasis and expression, be it because they had arisen from secular music (above all after the rise of the madrigal) or because they seemed incompatible with the restraint becoming to the divine service (since they tended towards the description and expression of personal feelings).

And what shall I say of thee, O Lorenzo Gusnasco … ? Of such renown were your musical instruments, Lorenzo, that when they were for sale in the principal cities of Italy and bore the inscription of having been made by Lorenzo da Pavia the client never hesitated, no matter how excessive the price might have seemed, to spend greatly because of the excellence and authority of this most famous maker.

The extraordinary dissemination of the Parisian repertory, resulting in its establishment in the thirteenth century as a kind of ‘Classical’ style (and later as an ars antiqua), was greatly abetted – if not made possible in the fist place – by what may have been an exclusively written mode of transmission. This is apparently the earliest body of polyphony to have been conceived, preserved and circulated entirely in writing. Equally important for the impact of the music of Paris, however, is the fact that it spawned a didactic tradition. It provided the foundation for a group of treatises that were the first to elucidate an already existing polyphonic repertory. Rather than instructing the singer how to generate polyphonic embellishments of plainchant ex tempore, these theoretical texts provided him with the information he needed to transform the written symbols in the manuscript before him into sounding music consistent with the intentions of the composer (or, at least, of the scribe), and they offered guidance to the organista wishing to create other works in a similar idiom. To be sure, these treaties did not transmit the Paris style intact.

The manuscript Munich, Bayerische Staatsbibliothek, Clm 14274 (now also ‘Tresorhandschrift l’) is a large collection of mensural polyphonic music, mostly composed in the first half of the fifteenth century, although a few pieces date back to the late fourteenth. Apart from its importance as a musical source (more than half the compositions it contains are unknown from other sources), Clm 14274 is the geographically northernmost representative of the small group of manuscripts from northern Italy and southern Germany which contain the core of the surviving repertory of early-fifteenth-century polyphony, and, as such, provides potentially vital documentary material for the study of this repertory.

It was Charles Hamm who first formalised the distinction between fifteenth-century manuscripts whose contents are arranged primarily according to liturgical type (introits, Kyrie settings, Gloria settings, etc.), in a more or less predetermined succession of gatherings, and those in which the repertory is more arbitrarily organised through small clusters of related works and in which gatherings tend to form separate and independently conceived entities. Trent 87 and 92 (hereafter Tr87 and Tr92) belong primarily to the second category. Haberl first distinguished them from the later Trent codices as an older group of manuscripts of independent origin; but it was Adler and Roller who recognised their important subdivisions. The main section of Tr92 (fols. 1–143) and the latter part of Tr87 (fols. 219–265), they noted, had each once formed a separate book,6 while the remaining portions of the manuscripts, TY87, fols. 1–218, and Tr92, fols. 144–268 (here referred to individually as Tr871, and Tr922 but jointly as TR?), were so closely related as to suggest that they belonged together.

The volumes of the Répertoire International des Sources Musicales (hereafter RISM) devoted to manuscripts of polyphonic music contain a nearly complete catalogue of the sources of late-medieval English polyphony known in the literature at the time of their publication in the late 1960s and early 1970s. Since that time a substantial number of new sources has been discovered or rediscovered.