Piano Concerto No. 24 (Mozart)

• 1. Introduction

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  Mozart's Piano Concerto No. 24 in C minor, K. 491, was finished on the 24th of March 1786. After hearing it in rehearsal, Ludwig van Beethoven turned to a colleague and said: "we shall never be able to do anything like that." Johannes Brahms called it "a masterpiece of art and full of inspired ideas." Musicologist Arthur Hutchings declared it, taken as a whole, Mozart's greatest piano concerto. What makes a work written in a single winter carry that kind of weight across two centuries? What structural choices did Mozart make here that he had never made before? And how did a piece born alongside a comic opera end up sounding like its opposite?

• 2. A Concerto Born in Shadow

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  Mozart was in his fourth season in Vienna when he composed K. 491, and it arrived as the third in a rapid cluster. He had already finished No. 22 in E major and No. 23 in A major; the No. 24 followed in a matter of weeks. Of all 23 original piano concertos Mozart wrote, only two are in minor keys. K. 491 is one; the other is No. 20 in D minor.

  Pianist and musicologist Robert D. Levin has argued that the concerto, along with its two predecessors, may have served as an outlet for a darker strand of Mozart's creativity during this period. The timing sharpens that argument. Mozart finished K. 491 just before the premiere of The Marriage of Figaro, a comic opera assigned catalogue number K. 492, one above the concerto's K. 491. Both were composed at nearly the same moment. The opera moves almost entirely in major keys; the concerto stays in C minor. Alfred Einstein, writing on the work, said it was hard to imagine "the expression on the faces of the Viennese public" when Mozart premiered it.

• 3. A Manuscript Left Incomplete

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  Musicologist Friedrich Blume attributed the notation errors scattered through the original score to Mozart having "obviously written in great haste and under internal strain." The solo part reveals why: Mozart intended to perform the work himself, so he simply did not write it out in full. On many pages he notated only the outer lines of scale passages and broken chord sequences. What went in the middle, he improvised.

  The score also carried no tempo markings at all. The speed of each movement is known only from entries Mozart made in his personal catalogue. Constanze Mozart sold the manuscript in 1800 to the publisher Johann Anton André of Offenbach am Main. Through the nineteenth century it moved between private collectors before the Scottish philanthropist Sir George Donaldson donated it to the Royal College of Music in 1894, where it remains today.

  Charles Rosen, the pianist and musicologist, found a structural clue in the manuscript's late additions. Mozart had substantially elongated the orchestral exposition during composition, adding the second subject of the first movement as a late insertion. Rosen argued this expansion was necessary because Mozart was building toward a solo exposition so long that the orchestral opening needed matching weight to balance it.

• 4. An Unprecedented Orchestra

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  K. 491 is scored for one flute, two oboes, two clarinets, two bassoons, two horns, two trumpets, timpani, and strings. No other Mozart piano concerto uses as many instruments. The clarinet was not yet a standard orchestral voice in the 1780s, and this concerto is one of only two Mozart piano concertos that combine both oboes and clarinets in the same ensemble.

  Robert D. Levin wrote that "the richness of wind sonority, due to the inclusion of oboes and clarinets, is the central timbral characteristic" of the work, and that "time and again in all three movements the winds push the strings completely to the side." The solo instrument is marked "cembalo" in the score, a term that normally signified harpsichord. Mozart used it here as a general label for the fortepiano, an eighteenth-century predecessor of the modern piano that offered more dynamic range than the harpsichord.

  The second movement strips the ensemble back sharply: the trumpets and timpani are silent for the entire Larghetto. Their return for the third movement gives the finale's C minor a harder edge than it would otherwise have.

• 5. Structural Radicalism in the First Movement

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  The orchestral exposition runs 99 measures, opening with the principal theme played in unison at a piano dynamic. The theme stays tonally ambiguous for 12 measures, not asserting C minor until its final cadence in the thirteenth. Across those 13 measures, it uses all 12 notes of the chromatic scale.

  When the piano enters, it ignores the principal theme. Instead it plays an 18-measure solo passage, after which the orchestra restates the theme and the piano picks it up only from the seventh measure. Donald Tovey called the solo exposition's introduction of entirely new secondary material "utterly subversive of the doctrine that the function of the opening tutti was to predict what the solo had to say."

  About 100 measures into the solo exposition the piano plays a cadential trill signaling a conventional close, but Mozart instead hands the woodwinds a new theme. The exposition runs for roughly 60 more measures before a second trill produces the real ending. Rosen called this a "double exposition" and linked it directly to the elongated orchestral opening: the two halves needed to match. The development opens with the piano repeating its entry to the solo exposition, a technique Mozart used in only one other concerto, No. 20 in D minor. Cuthbert Girdlestone described the stormy exchange between piano and orchestra near the center of the development as "one of the few occasions in Mozart where passion seems really unchained." Mozart did not write down a cadenza for the movement; among those who composed their own are Brahms, Ferruccio Busoni, Alfred Schnittke, and Gabriel Fauré.

• 6. Deliberate Simplicity in the Larghetto

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  Alfred Einstein wrote that the second movement "moves in regions of the purest and most moving tranquility, and has a transcendent simplicity of expression." The Larghetto is in E major and opens with the soloist alone, playing a four-measure principal theme before the orchestra repeats it. Michael Steinberg described the theme as one of "extreme simplicity"; Tovey called the fourth bar "naive" but argued that Mozart intended it so.

  Mozart's first sketch of the movement was considerably more elaborate. He simplified it to provide a stronger contrast with the intensity of the first movement. Girdlestone described the bridge passage connecting the movement's sections as "but a sketch," arguing that "to play it as printed is to betray the memory of Mozart." The overall structure follows an ABACA rondo pattern, nearly identical in form to the second movement of Mozart's Piano Sonata in B major, K. 570.

  Alfred Brendel, who recorded the concerto multiple times, identified two notation problems in the movement. One, in the middle statement of the principal theme, produces a harmonic clash between piano and winds that Brendel attributed to Mozart writing the two parts separately. The second is the time signature: played in cut common time, which calls for two beats per bar rather than four, the movement is in Brendel's view too fast.

• 7. Eight Variations and Their Aftermath

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  Arthur Hutchings considered the third movement "both Mozart's finest essay in variation form and also his best concerto finale." The first violins state the theme over string and wind accompaniment; it consists of two eight-measure phrases, each repeated, with the first modulating to G minor and the second returning to C minor. The soloist is silent until Variation I.

  Variations II through VI are what Girdlestone and Hutchings independently called "double" variations: within each one, every eight-measure phrase from the theme is further varied upon its repeat, following a pattern of AXAYBXBY. Variations IV and VI are in major keys; Tovey called the former, in A major, "cheerful" and the latter, in C major, "graceful." Variation V returns to C minor; Girdlestone called it "one of the most moving." Variation VII is half the length of the others, omitting the repeat of each phrase, and closes with an extra three-measure passage on a dominant chord that announces a cadenza.

  After the cadenza the soloist begins the eighth and final variation alone, with the orchestra joining after 19 measures. The final variation also brings a change in metre, from cut common time to compound duple time. Girdlestone pointed to the "haunting" effect of the numerous neapolitan-sixth chords in both the final variation and the coda, writing that the coda ultimately "proclaims with desperation the triumph of the minor mode." Pianist Angela Hewitt hears in the movement not a march, as Rosen argued, but a "sinister dance." That disagreement between two careful listeners about what the movement fundamentally is may be the best evidence of how much Mozart built into its 99 years of variations.