Yes, PJF, I'm working on this too. You're right, it's not as easy as it looks. My troubles begin on the second measure. The trill. I can't get it even enough...
...How does everyone else play these trills?
Please, call me Pete. (I need to edit my signature.)
The short answer is, play them with perfect alignment with the bass, as simply as possible within the constraints of tempo and the individual pianist, starting on the upper note, unless otherwise indicated. The more complete answer is, according to the Nathan Broder Edition (which I trust implicitly):
"The trills always begin on the upper auxiliary note, except when that note, in an appoggiatura, precedes the main note. The speed of the trill must be determined by the exigencies of each situation and the taste of the player. Where no after-turn is written out, the performer may play one or not. Where the after-turn is written out, it must of course be played. In rapid passages, where a normal trill is impossible because of tempo, a short trill or an inverted mordent may be used: eg, K330 Allegro Moderato, m. 129."
It is of great importance to understand the stylistic idiosynchracies of this sonata, et al. The sonata K330 (also K283, K332, K333, K545 and K570 ) is in "galant style (a style of "graceful elegance")." Mozart was most notably influenced by J. C. Bach's compositional style.
I found these two articles helpful.
"In music, Galant was a term referring to a style, principally occurring in the third quarter of the 18th century, which featured a return to classical simplicity after the complexity of the late Baroque era. This meant (in some implementations) simpler music, with less ornamentation, decreased use of polyphony (with increased importance on the melody), musical phrases of regular length, a reduced harmonic vocabulary (principally emphasizing tonic and dominant), and a less important bass line. It was, in many ways, a reaction against the showy Baroque style. Probably the most famous composer in the Galant style was Johann Stamitz.
Movement toward the preponderance of a homophonic texture in music had begun more than two centuries earlier, when composers started to insert sustained passages of homophony in their masses and motets to underline important portions of the text. It proceeded through the 16th century with the development of such generally homophonic vocal genres as the frottola and villanella in Italy, which led to monody and opera, the air de cour, air a boire and other continuo-accompanied songs in France, and the English lute song. Homophony grew popular during these years in instrumental music as well. Composed instrumental music seems to have consisted almost exclusively of transcribed chansons and other vocal works, or else the mere playing of such on instruments rather than singing them, until fairly late in the 15th century. In addition to this, however, existed a tradition of improvised dance-accompaniment music, and what early surviving instrument-specific compositions that are not of liturgical function follow in that vein. Indeed, a gulf between liturgical and non-liturgical instrumental music soon grew which was similar to that between the two vocal categories, though this was manifested more in form than texture.
During the 17th century, local schools of keyboard, plucked-instrument, and ensemble styles arose in France, England, and Italy, while the Germans tended to take stylistic elements from various sources. The stratification of melody and accompaniment that had been developing in vocal music also greatly influenced the instrumental; the two treble-plus-basso continuo texture of the Corellian trio sonata late in the century, for example, clearly derives from that of the earlier Monteverdian "concerto" for a few voices and continuo. It was in these local schools that emerged and congealed the characteristics called "galant," a style which was fully-fledged by the 1720s, and which, it is important to note, was recognised and referred to by this name in the writings of such contemporary commentators as Johann Mattheson (an important German theorist and composer), and Johann Joachim Quantz (composer and flute pedagogue).
Composers at least some of whose work can be described as galant include François Couperin, Jean-Philippe Rameau, and Jean-Fery Rebel of France, Giovanni Battista Sammartini, Baldassare Galuppi, and Antonio Vivaldi of Italy, the three most important Bach sons, Georg Philipp Telemann, and Johann Gottlieb Graun of Germany, and in England Thomas Augustine Arne, William Boyce, and John Stanley. As can be seen, perhaps, from some of these names, the galant style existed alongside of others, such as the lingering but increasingly retrospective high Baroque in all its national forms. As can equally be seen, the galant style was a driving force leading to the incipient "classical," or "Viennese classical" style to which point some works of Sammartini, Vivaldi, and C.P.E. Bach in particular among the above-mentioned composers. The German mid-18th century style arising from and sometimes synonymous with the galant is the Empfindsamer Stil, which in part led to the tendencies often called Sturm und Drang.
Grove's Dictionary of Music...
"During his first years in London, Bach made friends with the eight-year old Mozart, who was there as part of the endless tours arranged by his father Leopold for the purpose of displaying him as a child prodigy. Many scholars judge that J. C. Bach was one of the most important influences on Mozart, who learned from him how to produce a brilliant and attractive surface texture in his music. This influence can be seen directly in the opening of Mozart’s piano sonata in B-flat (KV 315c, the Linz sonata from 1783 – 1784) which very closely resembles that of two sonatas of Bach’s which Mozart would have known; and indirectly in Bach’s attempt in an early sonata (the C minor piano sonata, Op. 5 no. 6) to more effectively combine the galant style of his day with fugal music.
Johann Christian Bach died in London on the first day of 1782. Mozart said in a letter to his father that it was "a loss to the musical world." When Mozart first met J. C. Bach as a young boy, the two were described as "inseparable" by Mozart's father. They would sit at the organ, Mozart on Johann Christian's lap, both playing music for hour upon hour. It is often said by scholars that the music of Mozart was greatly influenced by Johann Christian. This is precisely why, in later years, Mozart would embrace the elder (Johann Sebastian) Bach's music as well. Johann Christian likely influenced the young Mozart in the forms of symphony and piano concerto. The spirit and sound of the young Mozart and J. C's music is remarkably similar. At the time of Bach's death, Mozart was composing his Piano Concerto No. 12 in A Major, K. 414; the Andante second movement of this concerto has a theme close to one found in Bach's La calamità del cuori overture. It has been suggested that Mozart's slow movement was intended as a tribute to JC Bach, his music, and his importance to Mozart's own work."
Encyclopaedia Britannica, Eleventh Edition