Dario Castello's Sonate concertate in stil moderno is a collection of 29 trio sonatas in two volumes, with 10 of them employing the sackbut. These works represent a significant repertoire for the sackbut in an era where specific instrumentation was only starting to become a convention. While these pieces are often studied, performed and recorded in Europe, most American trombonists are not aware of their existence. This study seeks to acquaint the American trombonist with the sonatas of Castello and to provide performance suggestions for those less familiar with this genre. Chapter 1 presents a survey of the current literature on Castello. Chapter 2 provides an historical background for music in Venice in the early 17th century, while Chpater 3 focuses on the composer and his music for sackbut. Chapter 4 investigages the sonata in early 17th century Venice. Chapter 5 provides an insight into early baroque performance practice by discussing principles such as affect, tempo, ornamentation, diminution and articulation. Examples from the ten sonatas are used to illustrate these principles, providing the modern trombonist with a framework in which to study Castello's music. The final chapter discusses the implications of this study on the American trombone curriculum.