C minor is traditionally the key of drama, passion, pathos, and pain, which also applies here in Mozart’s famous C minor sonata K. 457. He wrote it in October 1784, though what might have triggered this incredible outpouring of a “romantic” world of feeling is unknown.

Half a year later, Mozart composed his C minor fantasy K. 475, an extraordinary work in every regard. Both of these C minor works were published together in one edition in 1785, meaning that they were intentionally linked toget...