Although some of Wert's church music was published during his lifetime, much of it, being specially composed for the exclusive use of S Barbara, was not; to his contemporaries he was primarily known as a composer of madrigals and occasional pieces. Nevertheless, he wrote polyphony for S Barbara throughout his career, and a substantial corpus survives among the manuscripts from the basilica. Of his seven masses, only one, the Missa Dominicalis, was published during his lifetime. This appeared in a collection of six alternatim settings all based on the chant Kyrie orbis factor, and all by composers connected in some way or other with S Barbara and Mantua. Between them, these seven masses cover all the liturgical festal categories for which polyphonic masses are specified in the S Barbara Ceremoniale drawn up in 1583.
Of the various collections of hymns that were specially commissioned for S Barbara, Wert's magisterial cycle is the largest and most important. It consists of 127 pieces, none of which was published during the 16th century. In style, Wert's hymns resemble his other alternatim settings for the basilica; their extreme simplicity, evidently designed to allow the texts to be clearly heard, is reminiscent, in their combination of careful declamation, attention to text and restrained counterpoint, of the hymns and the Preces speciales of Jacobus de Kerle. Many of Wert's hymns were intended for performance on the feast days of saints who were prominent in the liturgy at S Barbara, and whose relics lay inside the Basilica (including St John the Baptist, St Sylvester, St Adrian and, of course, St Barbara herself); Marian feasts and the Finding and Exultation of the True Cross also receive special emphasis in Wert's hymn cycle.
Wert's motet settings, the most important and in some cases most widely circulated of his sacred music, were also the only part of this corpus to be printed in quantity in his lifetime. The Motectorum liber primus of 1566 contains 19 pieces, many of them settings of texts from the Roman liturgy. As with the Secondo libro de motetti (1581) and his third and final motet collection, the Modulationum cum sex vocibus liber primus of the same year, the majority of these are from Epistles, Gospels or Lectiones for major feasts. Taken in the main from New Testament sources, these extracts were traditionally read or intoned by the celebrant rather than sung in polyphony, as were devotional or psalm texts. This peculiarity may well be explained by the particular conventions of liturgical performance in S Barbara, where it is known that extra polyphonic items were often sung as substitutes for antiphons or other chants on major feast days. The motets apart, most of Wert's music for the basilica remained in manuscript as a private and reserved repertory specifically composed for a single privileged and élite institution. Partly proclaimed through the deployment of special texts (at least two of the hymns were written by Marc' Antoine Muret) and cantus firmi derived from the S Barbara liturgy, its distinctiveness was additionally underscored by being set in alternatim fashion.
Although Wert's task as maestro di cappella at S Barbara must have occupied a good deal of his time, he was largely known to the outside world as a composer of madrigals. The dedications of his published books shadow his biography: the early ones were addressed to Count Alfonso Gonzaga, Duke Ottavio Farnese, Consalvo Fernandes di Cordova (Governor of Milan), the Marchese di Pescara and Duke Guglielmo Gonzaga. Il quinto libro of 1571 is the only collection to be dedicated to a collective patron, in this case the members of the Accademia Filarmonica of Verona; and from the sixth book on, the dedicatees are mostly members of the Gonzaga family. Two books are addressed to Vincenzo Gonzaga, one to Vincenzo's wife Margherita Farnese, one to his mistress Agnese Argotta (who was much involved in the attempts to stage Il pastor fido in 1591–2), and one to his second wife Leonora de’ Medici. Indeed the idea that Wert, as the Gonzaga composer par excellence, had embarked on a plan to dedicate each of his madrigal books to a different member of the family, is explicitly stated in the dedicatory letter to L'undecimo libro. The only real exception to the pattern is L'ottavo libro, dedicated to Duke Alfonso II d'Este and filled with madrigals written for the celebrated Ferrarese concerto delle dame.
Wert's madrigals follow a discernible pattern of stylistic change, mirroring both the resources available and the differing tastes of his patrons, as well as his exposure to other musical influences. In their use of chromaticism, representational melodic figures and dark colouring the early books are strongly indebted to Rore, whom Wert knew personally. From Il quarto libro onwards these characteristics undergo a process of refinement, and are now combined with an increased use of pure homophony and an interest in textural contrast. Il sesto libro contains two long canzoni written in the declamatory style that writers since Einstein have identified as one of Wert's most important and original contributions to madrigalian language. The texts which Wert set in these books are characteristic of mid-century taste; Petrarch's verse is prominent, there is some Bembo as might be expected and, less predictably, a good deal of Tansillo.
The real change comes with Il settimo libro, a book which marks his increased involvement in the life of the Ferrarese court, and his new enthusiasm for epic verse and in particular for the works of Tasso and Guarini. This, and the two books that follow it, are filled with pieces in a more dramatic style, forged out of the language of strong contrast and theatrical melodic gesture. The pieces of the eighth book show the virtuoso upper lines and separation of upper and lower voices into separate blocks that would become the hallmark of madrigals written for the concerto delle dame, much copied by other composers working in the Mantuan–Ferrarese orbit during the 1580s and 90s, including Benedetto Pallavicino and Claudio Monteverdi. Wert's book of five-voice villanelle, his only collection of pieces in a lighter vein, is much less distinctive in style, being virtually indistinguishable from Marenzio's in the same genre. L'undecimo libro, the last of Wert's collections to appear during his own lifetime, contains a number of settings of passages from Il pastor fido; they obviously reflect the intense interest in this play at the Mantuan court in about 1591, but the temptation to identify the book’s eleven settings with music written for the Mantuan production must be resisted. Mannered, aristocratic and elegant, the poetry of Il pastor fido came to rival that of Tasso's Gerusalemme liberata as a source of madrigal texts. In this, as in so many other ways, Wert's madrigals are innovatory and prophetic, introducing elements of style and gesture that historians usually associate with later composers, and above all with Monteverdi who spent his earliest years at Mantua during Wert's final ones.
Wert, Giaches de
For works mentioned in Wert's letters which cannot be identified see Fenlon, Letters and Documents (1999).
all printed works except anthologies published in Venice
Edition: Giaches de Wert: Collected Works, ed. C. MacClintock and M. Bernstein, CMM, xxiv (1961–77) [W]
Wert, Giaches de: Works
Il primo libro de madrigali, 5vv (1558) 
Il primo libro de madrigali, 4vv (1561) [1561a]
Madrigale del fiore, libro primo, 5vv (1561) [1561b]
Madrigale del fiore, libro secondo, 5vv (1561) [1561c]
Il terzo libro de madrigali, 5vv (1563) 
Il secondo libro de madrigali, nuovamente con nuova giunta ristampati, 5vv (1564) 
Il quarto libro de madrigali, 5vv (1567) 
Il quinto libro de madrigali, 5vv (1571) 
Il sesto libro de madrigali, 5vv (1577) 
Il settimo libro de madrigali, 5vv (1581) 
L'ottavo libro de madrigali, 5vv (1586) 
Il nono libro de madrigali, 5vv (1588) 
Il primo libro delle canzonette villanelle, 5vv (1589)