The sonata Kv.301 in G major is probably the most known of the whole set of KV.301-306 It is regularly performed and one can already see some minor changes after Mozart got inspired from the duets of the German composer Joseph Schuster. The piece, like five of the six of this set, has only two movements.
The first movement starts with the violin having the main line and the piano accompanies. Unlike KV.296 where the main theme repeats twice after each other, in this sonata the main melody has a more extensive line. A short bridge of 4 bars gives a contrast and brings us back to the piano part which has the main melody with the violin accompanying exactly the same thing as the right hand of the piano. Mozart wrote some nice canonic parts in this piece which really show a more communicative way of musicking than he did before. Also, the treatment of the instruments with the melodies at the same times is more complex than before. The violin definitely got a bigger role in this sonata compared to the youth-works and the sonata Kv.296.
The second movement is an Allegro in 3/8. It is written in an A-B-A style with the middle part being in G-minor. The first part has a very dance-like character to it and both instruments keep the same equality in melodic lines. Especially the second section of the first part is interesting to look at, the instruments move in different directions and cross each other in pitch from time to time making both instruments equally important. The minor part is composed in a "Siciliana" style where only the violin plays the melody. It is often performed a bit slower than the first section A. The second and more extended part is in the relative major and finishes back into the original key of G minor before going back to the A section.