Mozart’s comments on the musical style of his piano concertos (K. 413-415) portray his underlying aesthetic principle that music should be clear and accessible:
I still have 2 concertos to write to complete my subscription concerts. – These concertos are a happy medium between what’s too difficult and too easy – they are Brilliant – pleasing to the ear – Natural without becoming vacuous; – there are passages here and there that only connoisseurs can fully appreciate – yet the common listener will find the satisfying as well, although without knowing why.” (1)
(1) Mozart, in a letter to his father, 28 December 1782. Cited in: Spaethling, Robert (2000) Mozart’s Letters; Mozart’s Life. London: Faber and Faber, p.336.