Mozart's Ave Verum Corpus and Eighteenth-Century Musical Style

Among the most fascinating qualities of Western music is its harmonic language, with its tensions and dissonances, contests and progression. By establishing a home base (the tonal center or key) the harmonic world of Western music is one in which consonance is defined by the dissonance it creates. By choosing a point of reference one necessarily identifies any other point as foreign, even in competition with the referential. This basic tension between "home" and "away" is found in the very notion of the key, where the expectation that the tonic harmony will govern the departure and closure of any given piece is elemental to the language of every composer from Bach to Brahms. This dichotomy is so fundamental to the Western musical tradition that the opposition of two polar pitch loci was already an important part of plainsong pitch organization. (1) The hierarchical tonal system thrives on the expectation that the tonic and dominant harmonies will have special prominence. Other harmonies depart from the tonic and return through the dominant in normal patterns and cadences. In the eighteenth century, the possibility of reinforcing or thwarting these expectations gave composers great communicative powers, aided by the post-baroque, melodic, periodic style. It is in the special moment of the late eighteenth century, when a pan-European style built on the mature Western tonal system had taken hold, that Mozart produced the music that would for centuries live on in cherished ubiquity. This article will further examine the harmonic style of the period, followed by a brief analysis of Mozart's Ave Verum Corpus, KV618, that will explore the interaction of its musical structure and text. SONATA STYLE The term "sonata style" was coined by Charles Rosen as a way to identify the shift in instrumental composition from the sectional, ornament-heavy music of the Baroque toward a style concerned with a simple surface texture wedded to a continuous, linear and dramatic structure. (2) The new style communicated with the listener almost linguistically, leading from one well-defined idea to another through a series of stable and unstable harmonic regions. A basic assumption of the style is that the surface ideas gain their importance through the underlying harmonic progression. Because of the logic of the musical process itself, sonata style created forms that were "completely written out (unlike the da capo aria which left the decoration to the singer), its shape was always definable by a simple contour (unlike the additive and easily extensible forms of the concerto grosso and the variation), and it was totally independent of words (unlike the madrigal and the opera)." (3) [ILLUSTRATION OMITTED] The trajectory of a sonata style piece involves five basic harmonic motions in the following order: 1) establishment of a home key, 2) departure from the home key, 3) establishment of a secondary key, 4) motion back to the original key, and 5) reestablishment of the original key and final cadence without departure. Naturally, the proportions of these motions vary in late eighteenth-century pieces, and the fluidity of formal procedures should be stressed. (4) For instance, the motion to a secondary key may not be terribly elaborate, consisting only of a common chord modulation between periods. However, the contrast between two or more tonal centers and the basic alternation of stable and unstable sections is a convention of the style. Stability is achieved by harmonic clarity (one knows what key one is in) and clear phrase structure (one knows the tune one is supposed to whistle). Instability is marked by modulation, sequence and a lack of periodicity. Thematic material is found in stable sections, while unstable sections tend to make use of motivic imitation, fragmentation, and figuration. The two basic types of sections (stable, thematic areas contrasting with unstable, non-thematic areas) are what give sonata style the ability to be declamatory, confrontational, tuneful, contradictory, expansive, and conversational all within one piece. …