J.C. Bach - Keyboard Sonata Opus 5, No. 5 In E Major

Johann Christian Bach was fifteen when his father Johann Sebastian Bach died in 1750.  He went to Berlin to finish his studies with his elder half-brother C.P.E. Bach and while he was there he made his reputation as a keyboard player, especially of his older brother's works. About 1754 he moved to Italy where he immersed himself in the music and culture of the country to such an extent he converted from the Lutheran religion to Catholicism. He also began to change his style in composition from his older brother's to a style derived from his travels in Italy as well as France and England.

He originally intended to stay in England about a year when he first visited  in 1762 to stage some of his operas. His music became very popular, especially with the royal court, and he ended up living there until his death in 1782. He met the young Mozart in London in 1764 and his compositions became an influence on Mozart.

Bach began to favor the piano over the harpsichord early on, and was possibly the first performer to play on the instrument in public in England. English pianos of the time were known for their craftsmanship and innovations that gave the instrument a fuller tone and more reliable action. Haydn came to prefer English pianos also, as did Beethoven. Bach's Opus 5 consists of 6 sonatas that are designated for pianoforte or harpsichord, most likely because this was a period of transition between the two instruments and publishers naturally wanted to get as many sales as possible.  Modern day performances of the sonatas vary in the type of instrument used, just as the original printing intended. It is up to the performer to make the music 'speak' according to the instrument it is being played on.

The 5th sonata in the Opus 5 set is in three movements:
I. Allegro assai -  The movement begins with a rapid-fire figure that begins in the bass in eights notes and has the right hand enter to chase it after a sixteenth note rest. This continues for 4 measures. The bass then continues in a running wave of sixteenth notes as the treble plays a melody that is also peppered with sixteenth notes. This continues until a B major chord is reached which signals the start of the second subject which is in the dominant key of B major. The second subject is slightly more leisurely in the beginning but it soon takes off running with sixteenth notes and comes to a close on a B major chord. The exposition is repeated. The development starts with the figure from the beginning played in B major. Other material is developed, modulations occur, and the music returns to the home key of E major. During this early phase of sonata form it consisted of two parts to be repeated, the exposition and the development.

II. Adagio - This slow movement is in the key of A major with a steady broken chord accompaniment.

III. Prestissimo - A rondo with a rhythmic recurring subject. The first episode flirts with B major, the next  is in E minor. The subject reappears verbatim. The last episode modulates into related minor keys, the subject returns one last time and comes to a close.