Sonata in G Major

The first movement of Mozart's Piano Sonata No. 5 in G Major is an example of a piece in sonata form, a structure developed from rounded binary form which is commonly used throughout, and even after, the classical period. It is comprised of an exposition, development and recapitulation, with two subjects, forming a very structured piece reminiscent of the classical music of the time.

The piece begins with the exposition, which introduces the first and second subjects to the listener for the first time. It begins with the first subject at the start of the piece without an introduction and showcases a few identifiable musical ideas, such as the dotted quaver and semiquaver rhythmic pattern in the right hand with an Alberti bass-like accompaniment in the left hand, and fast semiquaver scale runs such as in bars 8-9 and 14-15. This is followed by a transition beginning in bar 16, an ascending pattern which cleverly disguises a modulation to the dominant, D major, by sharpening the subdominant note of the scale, in this case the C# in bar 21. This modulation leads into the second subject of the exposition, a section contrasting with the first subject in key and new musical ideas - for example, the syncopated right-hand melody in bars 23-24 and 45-46, or the chromatic descending pattern in bars 33-34 and 38-39. These contrasting melodic ideas accompany the modulation in key to clearly distinguish between the two subjects, making it obvious which subjects are being referred to during the development and recapitulation later in the piece. The second subject is rounded off by a codetta in bars 51-53 before a repeat back to the start, completing the exposition.

After the repeat, the key of D major from the second subject carries over into a short development section, which explores the tension created by the contrasts between the first and second subjects. It begins with eight bars of new, original material still in the dominant key, and has a different energy to the first and second subjects - it has a lighter, dance-like feel with frequent grace notes and no emphasis on the first beat of the left hand. In sonata form, the development commonly references and develops on motifs introduced in the exposition, however it appears to act almost like a third subject in this piece. From bar 62 onwards, there is another transition - this time modulating back from the dominant (D major) to the tonic (G major) by flattening the sharpened C in bar 63.

This leads us into the recapitulation, which usually repeats the exposition in full but without modulating in the transition between the subjects. The recapitulation in this piece borrows some properties from a development in a standard sonata form during the first subject and repeats the second subject in the tonic key. The phrase in bars 71-75 remains the same, but when the musical idea is repeated in bars 75-79 it has modulated from G major to A minor by sharpening the G note. This is the relative minor of C major, which in turn is the subdominant of G major. A more complex modulation such as this is most common in the development, however due to the development acting similarly to a third subject in this piece, this was implemented into the start of the recapitulation instead. The transition from the exposition repeats in bars 83-89, however the second subject at bar 90 begins back in the tonic key of G major, instead of the dominant key which the transition led up to. The second subject repeats in full from bars 90-118 but down a fifth in the tonic key, and the codetta at the end now serves as a coda in bars 118-120, completing the piece.