IN MEDIAS RES
I wish my father or my mother had minded what they doing when they conceived me; had they considered how much depended upon what they were doing, I should have made a quite different figure in the world: thus begins (slightly paraphrased) Laurence Sterne’s celebrated novel, Tristram Shandy (1759). The narrator of this book argues that his own strange beginning has had an impact on his entire life, and throughout the novel he continues to obsess over the peculiar conditions of his birth. Though few of us are so obsessive, most would agree that an unusual beginning could have strong ramifications, not only in life, but in art as well.
In many a work of music, for instance, an odd opening can have repercussions that are felt throughout the composition. This is often the case when a piece begins on a non-tonic chord. Most tonal compositions, of course, start with a statement of the tonic chord, or at least they start with an implied tonic. A tonic opening most logically establishes a point of tonal departure; it provides an area of stability against which subsequent harmonic developments may be contrasted. A non-tonic opening, on the other hand, can evoke a sense of disorientation, causing a composition to begin as though it were in the middle of something. Its unusual nature helps highlight the non-tonic opening, making it ripe for motivic elaboration. In many compositions, a pronounced opening gesture will in turn relate to subsequent events, and this is particularly true of works with non-tonic beginnings. Indeed, in such works, the musical implications of the non-tonic opening often play a central role throughout.
Non-tonic openings gained special popularity in the nineteenth century, and they may occasionally be found in compositions of the late eighteenth century as well. A number appear in works of such composers as C.P.E. Bach, Haydn, and especially Beethoven. In fact, over one-third of Beethoven’s instrumental works contain at least one movement with an off-tonic beginning, including a movement from his earliest official publication, Op. 1, No. 1.
One composer who avoided such beginnings, however, was Mozart. Almost all of Mozart’s instrumental works begin with a clearly stated tonic, or at least they begin with a sonority that might suggest a tonic chord. Of all of Mozart’s instrumental movements, only one starts with a substantial and unambiguous non-tonic opening: the second movement of his String Quartet K. 160.  Yet in this lone work, Mozart handles the opening and its consequences with amazing skill. As a result, this piece may well be regarded as a model of how one may exploit the possibilities afforded by a non-tonic opening.
The second movement of K. 160 begins with the progression VI7-II-V7-I (=V7/II-V/V-V7-I, a chromatically inflected cycle of fifths). Taken by themselves, these chords are by no means unusual. For instance, in the second movement of Beethoven’s Fifth Symphony, a similar chord succession appears in bars 5-6, where it lies comfortably within a larger progression.
Example 1: (a) Beethoven, Symphony No. 5 in C Minor, Op. 67, II, bars 1-6 (example of VI-II-V-I within the midst of a progression).
On the other hand, these same chords would produce a bit of a surprise if they were to arise at the beginning of a progression. Nevertheless, perhaps to take advantage of this sense of surprise, a number of second themes by Mozart start precisely in such a manner. In K. 160, however, the effect is even more extraordinary, for here the progression appears at the very beginning of the piece, so that the entire movement seems to start in medias res.
Example 1b Mozart, Quartet for Strings in E-flat Major, K. 160, II, first theme, bars 1-6.
In addition to delaying the entrance of the I chord, the opening progression in this movement also obscures the tonic key. Since the movement begins with a series of applied dominants, its central key is not apparent until bar 2 (and it is not confirmed until the perfect authentic cadence in bar 6); only retrospectively are the initial harmonies understood to lie within the key A-flat major. That this is the second movement of a larger work does not necessarily eradicate the opening tonal ambiguity. After all, it surely would have been possible for an E-flat major work to have a second movement that is in the key of B-flat major (the key that is tonicized in bar 1).
The odd effect of the opening is even further aggravated by the dissonant setting of the first diatonic notes of the melody, E-flat and D-flat. These notes, which form the first tones of the opening linear progression, initially arise as chordal sevenths.
Example 1c, Voice-leading sketch of exposition, bars 1-22.
Significantly, this situation is "corrected" in bars 4-5, where an
E-flat and D-flat reappear within a consonant setting. Immediately following
this, there is a firm cadence in A-flat major, along with a straightforward
prolongation of the tonic, as though to counter the opening ambiguity by
strongly confirming the main tonality.
The resulting sense of stability is not to last long, however, for elements from the harmonically disturbing non-tonic opening come back to haunt us at the very outset of the second theme group. The second theme, like the first, also starts on a non-tonic chord.
Example 2, Bars 12-15.
Curiously, its opening harmonies are similar to the ones that began the first theme, though now functioning within the key of E-flat. That is, the chord succession of an F dominant seventh resolving to a B-flat chord that was seen in bar 1 returns in altered form in bars 13-14, now functioning as a V/V to V in its new context. Owing to its position within the form, it is easy to hear the motivic connection of the F7 chord of bar 13 with the F7 chord of the opening measure.
The sudden entrance of the second theme accentuates its shocking effect. The preceding transition section ends in bar 12 with a half cadence in the original key of A-flat, creating a so-called "bifocal close." Typically, a bifocal close is followed by a break of some sort, thereby articulating the cadence before proceeding to the second theme group. Here, however, there is no such break; rather, the half cadence is immediately followed by an ascending stepwise motion in the cello and viola. This motion seems to lead toward a return to A-flat, or at least toward a return of the opening theme. The expected return is thwarted, however, as the instruments all precipitously shift registers to herald the start of the second theme. The abruptness of this shift is further underlined by a sudden change of texture and dynamics. As though in reaction to this brusque return of the opening harmonies here, the first violin subsequently twice returns to the opening motive (in bars 17 and 18), each time accentuated by a sudden increase in dynamics.
The unusual opening harmonies also relate to events within the recapitulation. Significantly, the bridge section of the recapitulation is altered from its prototype in the exposition. Note that the changes here were not prompted by the key design of the recapitulation: since the transition has a bifocal close, bars 1-12 could have returned verbatim at the beginning of the recapitulation. Mozart avoided such a facile solution, however, altering the transition in bars 36-40 so as to revisit (in expanded form) the chord progression from bars 1-2. In bars 36-40, however, these harmonies do not come at the beginning of a phrase (as was the case in bars 1-2 and 13-14 of the exposition), but rather are embraced within a larger progression.
Example 3 Bars 36-40.
The second theme group likewise is radically changed when it returns within the recapitulation. Here, too, the changes relate to the progression found at the beginning of the movement. As in the preceding transition section, the harmonies from bars 1-2 are recast in bars 45-47 so as to appear in their "proper" context within the middle of a progression.
Example 4(b) Voice-leading sketch of recapitulation.
As suggested earlier, the harmonies at the beginning of the movement seem as though they belong in the middle of something. As though in reaction to this, the recapitulation actually does place the opening harmonies within the middle of something, thereby creating a type of rapprochement. As such, the recapitulation in a way resolves some of the harmonic/formal conflicts presented in the opening of the movement.
* * * * * *
Throughout its course, this work—like Tristram Shandy—seems to struggle to come to grips with the odd features of its unusual beginning. The manner in which the motivic reflections of the opening recur throughout seems to unfold a type of drama. At times these motivic parallelisms come as though in a disturbed reaction to the opening progression, as in bars 13-14. At other times, a sense of reconciliation is produced as elements from the opening gesture return within a more normal setting, as is the case in bars 4-5 or in the recapitulation.
Strategies similar to the ones seen here may be found as well in many other pieces that have non-tonic openings. What is so remarkable is that Mozart was able to seize upon these possibilities in this early composition, his only clear attempt to use a substantial off-tonic beginning. Through such means, he was able to create a composition of powerful dramatic force, one that foreshadows strategies seen in the works of later generations of composers.
 To be sure, there are some instances of incidental non-tonic openings in Mozart’s oeuvre, as in those pieces that begin with a quick V-I progression starting on an upbeat (such as the Quartet for Strings K. 575, III). There are also Trio sections by Mozart (such as the one from the “Jupiter” Symphony, K. 551) that begin on a non-tonic chord, though such sections surely must be considered to arrive in the middle of a larger Menuetto-Trio movement. Furthermore, some of Mozart’s pieces strongly suggest a non-tonic opening but begin with a rest in the bass, thereby creating at least some doubt as to the identity of the opening sonority (see, for instance, the Sonata for Piano K. 281, III). Yet in no other work of Mozart is a non-tonic opening nearly as clear and substantial as in the second movement of K. 160.
 See, for instance, Mozart's Sonata for Piano in C major, K. 279, I, bars 17-20, or his Sonata for Piano and Violin in B-flat major, K. 378, I, bars 30-33.
 Heinrich Schenker argues that when a descending fifth progression in the upper voice is supported by an auxiliary cadence (that is, a progression that begins on a chord other than a root-position I), the tonic will appear only at the conclusion of the linear descent: any tonic that arises before the conclusion of the linear progression should be regarded as a type of anticipation; see discussion in Free Composition, translated and edited by Ernst Oster (New York: Longman, 1935), Par. 219 (pertaining to Fig. 93) and Par. 245 (pertaining to Fig. 110a). Following Schenker in this regard, in the sketch of Example1c I show the initial tonic chord as arriving fully only in bar 6, with the tonic chord of bar 2 functioning as a type of anticipation (compare my Example1c with the Figure 154,1 from Schenker’s Free Composition). For similar reasons, I read as a type of anticipation the local tonic chord of bar 17 (see Example 4a), as I do the tonic chord of bar 51 (see Example 4b).
 A "bifocal close" refers to a transition section that concludes on the V chord of the original key in both the exposition and the recapitulation. (It is "bifocal" because the same cadence can occur--without transposition--in both places. In this sense, a sonata form movement with a bifocal close is unlike the more typical movement in which the transition section of the exposition ends with a cadence on V of the new key and thus must be transposed when it recurs in the recapitulation.) The term was coined by Robert Winter in "The Bifocal Close and the Evolution of the Viennese Classical Style," in The Journal of the American Musicological Society 42/2 (Summer 1989), pp. 275-337.
In responding to the daringness of this passage, performers might try
to enhance the deception of bar 13 by preceding it with a decrescendo and
attacking the opening of this measure a bit early, but however one chooses to
approach this passage, surely sensitivity to the surprising nature of this
passage is needed. Unfortunately, the early works of Mozart often are played
with a misguided sense of elegance and refinement that can rob the music of
its excitement. For effective renditions of this music, it is important for
performers not to overlook the boldness of passages such as the one seen in
bar 13 of this quartet.
 In fact, in about one third of his sonata form movements in which there is a bifocal close--including the very first movement of K. 160--Mozart actually does repeat the first theme and transition section verbatim during the recapitulation. His decision to rewrite the bridge section here, therefore, must have been a deliberate choice.