Seventeenth century musicians delighted their audiences by writing music both predictable and unexpected, both stable and fluid. In the former, pieces such as grounds, with their repeating bass lines rely on regularity for their structure. In the latter, sonatas and preludes are products of the most free and unrestrained manner of composition. Belladonna performs works by Castello, Cabanilles, Schmelzer, Destouches, Sances, Becker and Merula, contain these contrasting qualities, often within a single piece.