This lecture introduces the vital concept of instrumental musical form—preordained processes that organize musical materials into recognizable structures without the presence of (or need for) words. Until the Baroque Era, almost all musical form was determined by the words being set to music. The development of instrumental music during the Baroque Era went hand-in-hand with the creation of musical structures that would render abstract instrumental music intelligible to its audiences. This lecture focuses on Baroque-era musical forms based on the process of variation: passacaglia, ground bass, and chaconne (or ciacona). We will revisit “Dido’s Lament” from Purcell’s Dido and Aeneas as an example of a passacaglia, and we will examine Bach’s magnificent Passacaglia in C Minor for Organ.