'''Piano Concerto No. 15 in B-flat major''', KV. 450 is a concertante work for piano and orchestra by Wolfgang Amadeus Mozart. Mozart composed the concerto for performance at a series of concerts at the Vienna venues of the Trattnerhof and the Burgtheater in the first quarter of 1784, where he was himself the soloist in March 1784.
In a letter to his father, Mozart compared this concerto with the 16th concerto in D:
"I consider them both to be concertos which make one sweat; but the B flat one beats the one in D for difficulty."Hutchings (p. 290)
Indeed, many pianists consider this to be one of the more difficult of Mozart's piano concertos.Steinberg The concerto is primarily difficult from its many quick scale patterns which must be played perfectly and also from its many fast chord patterns moving up and down. Beginning with this concerto, Mozart began to use the term "grand" to describe his concerti such as K.450 which feature a prominent and required wind section for the ensemble.Keefe, Simon P., ''The Cambridge Companion to Mozart''. Cambridge University Press (2003, ISBN 0-521-80734-4), p. 88.
The work is orchestrated for solo piano, flute, two oboes, two bassoons, two horns, and strings. The concerto is in three movements:
# ''Andante'' in E-flat major
Diana McVeigh has commented on the division of musical themes in the concerto's first movement, in the context of the relationship between soloist and orchestra. The finale follows the even rondo form.
Simon Keefe has noted contemporary comments from Mozart's era on how the woodwind writing in this concerto showed a "newly intricate and sophisticated" character compared to Mozart's prior keyboard concerti. Keefe has also analysed the character of the dialogue between the soloist and the orchestra in the concerto's first movement. Elaine Sisman has postulated that Mozart modeled the slow movement on a theme-and-variations movement from the Symphony No. 75 of Joseph Haydn.