Chaconne and Passacaglia
The chaconne has been understood by some nineteenth and early twentieth-century theorists—in a rather arbitrary way—to be a set of variations on a harmonic progression, as opposed to a set of variations on a melodic bass pattern (to which is likewise artificially assigned the term passacaglia), while other theorists of the same period make the distinction the other way around. In actual usage in music history, the term "chaconne" has not been so clearly distinguished from passacaglia as regards the way the given piece of music is constructed, and "modern attempts to arrive at a clear distinction are arbitrary and historically unfounded." In fact, the two genres were sometimes combined in a single composition, as in the Cento partite sopra passacagli by Girolamo Frescobaldi, and the first suite of Les Nations (1726) as well as in the Pièces de Violes (1728) by François Couperin.
Frescobaldi, who was probably the first composer to treat the chaconne and passacaglia comparatively, usually (but not always) sets the former in major key, with two compound triple-beat groups per variation, giving his chaconne a more propulsive forward motion than his passacaglia, which usually has four simple triple-beat groups per variation. Both are usually in triple meter, begin on the second beat of the bar, and have a theme of four measures (or a close multiple thereof). (In more recent times the chaconne, like the passacaglia, need not be in 3/4 time; see, for instance, Francesco Tristano's Chaconne/Ground Bass, where every section is built on seven-beats patterns)
A chaconne's bass line—let alone the chords involved—may not always be present in exactly the same manner, although the general outlines remain understood. (Handel's "Chaconne" in G minor for keyboard has only the faintest relationship to the understood form.)
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