AGAZZARI, AGOSTINO. - Musician, born in Siena on 2 Dec. 1578, died there on 10 Apr. 1640. Chapel master, first at the Collegio Germanico in Rome from 1608 to 1630, then at Siena Cathedral from 1630 until his death, he was of great importance for the dissemination of the basso continuo, of which, together with Banchieri, Bianciardi, and Ludovico Grossi da Viadana, he was one of the earliest advocates and whose foundations he set forth in a fundamental theoretical work that is also regarded as the first true treatise on instrumentation: Del sonare sopra'l basso con tutti li strumenti e dell'uso loro nel conserto (Siena, 1607).
Another of his theoretical works, on sacred music in conformity with the Council of Trent, is La musica ecclesiastica, dove si contiene la vera diffunzione della musica come scienza non più veduta e sua nobiltà (Siena, 1638). As a composer he left an extensive body of sacred works, including 4 books of Sacrae Cantiones for 2 to 8 voices (1602–1606), various collections of Psalms (1609, 1610, 1611, 1612), Missae quattuor (for 4, 5, 8 voices, Venice, 1617), Stille soavi di celeste aurora a 3, 4, 5 voci col basso per sonare (Venice, 1620), «Eucharisticum melus» (Rome, 1625), Litanie della B. V. M. (Rome, 1639), etc. Some compositions have modern editions in Proske’s Musica Divina (IV: Stabat Mater), and a facsimile of the 1607 treatise has been published by the Bollettino Bibliografico Musicale of Milan.