In the 18th century, the concerto was transformed into a viable instrumental genre to demonstrate both virtuosity and a cohesive character that embodied naturalness. Although the series of changes from the Baroque concerto Grosso to the Classical concerto was gradual and cannot be attributed to a single composer, the Piano Concerto no. 20 in D minor K. 466 by Wolfgang Amadeus Mozart is a deft representation of the genre as an era. Of particular interest in this concert is the treatment of sonata form in the first movement. Compared to other instrumental genres of that era, a tangible gap exists between the concerto sonata form and that of other instrumental genres such as the symphony. To understand this categorization, one must look beyond the boundaries of genre and form and focus on the function of each individual work. As Charles Rosen suggests, “By treating the sonata not as a form but as a style – a feeling for a new kind of dramatic expression and proportion – we can see how the functions of a concerto adapt to a new style.” It is with this interpretation that I intend to explore how the functions of a concerto, including the display of virtuosity and the contrast of two types of sound, make the first movement of K. 466 with the potential to eclipse any attempts at categorization with other genres. of the classical period that use the sonata form. The sonata form, according to the Oxford Companion to Music, is the most important musical form of the classical period. The sheet is made up of three distinct sections, exposition, development and recapitulation. In genres such as the symphony or string quartet, the sonata form has not strayed from this general pattern. The classical concert... center of the sheet... Oxford Music Online. Accessed 14 November 2011. http://oxfordmusiconline.com.Hadow, WH Sonata Form. London: Novello, 1979. Harutunian, John Martin. Sonata styles of Haydn and Mozart: a comparison. Lewiston, New York: E. Mellen Press, 205.Mozart, WA “Piano Concerto No. 20". K. 466. In Wolfgang Amadeus Mozarts Werke, Serie XVI:Concerte für das Pianoforte. Leipzig: Breitkopf & Härtel, 1878, 181-236. http://imslp.info/files/imglnks/usimg/a/a9/IMSLP26334-PMLP15389-Mozart_Pf_Concerto_20_K466.pdf (accessed 24 November 2011). Rosen, Charles. The classical style: Haydn, Mozart, Beethoven. London: Faber and Faber Limited, 1971. Tucker, G. M. and Nicholas Temperley. Oxford Companion to Music. Oxford: Oxford University Press, 2002.Webster, James. “Forma Sonata”. Grove Music Online. Accessed November 14, 2011. www.oxfordmusiconline.com.