knowing why." Two years later (1784) he wrote, "I cannot make a choice between the two concertos in B-flat and D. Either one will make the player sweat." The distinguishing merit of these compositions for pianoforte and orchestra, unjustly neglected in these days, is the combination of the two different forces, while these forces at the same time preserve their individuality. Instead of a duel to the death between the instrument and the orchestra, there is a generous appreciation of the qualities and limitations of the pianoforte, which in Mozart's time was still weak in mechanism. Therefore one gives way to the other for the effect of the whole. The orchestra enters not to crush but to support. Often the pianoforte part seems absurdly simple, but a closer investigation will show that this simplicity is most artfully designed and intended. Seldom are important themes given to the pianoforte or orchestra alone; they are shared generously. And no words can reproduce the colors of the orchestral tone-paintings, or describe the marvelous results gained by simple means and an unerring instinct. The first movements are in the sonata form, but there is a certain freedom, and the proportions are on a larger scale. There is a cadenza, invariable, at the conclusion, and Mozart in his concerts excited wonder by his improvisations. The cadenzas published were for the use of pupils. The second movement is in song-form, full of sentiment, often romantic, the expression of temperament; the song is sometimes varied. The last movement is generally in rondo form, and the influence of the dance is strongly marked. These movements are gay and graceful, and occasionally there is a touch of Haydn's humor. The greatest of these concertos are perhaps those in D minor (K. 466), C (467), C minor (491) and in C (503). Nor among his pianoforte works must the two pieces originally written for a musical clock be forgotten, which are only now known by a four-hand arrangement. The pianoforte works of Mozart are much neglected in these days, and most unjustly. It is the fashion to call them simple and antiquated. But the best of the concertos and the sonatas make severe demands upon the mechanism and taste of the pianist; the apparent simplicity is often a stumbling block to him that eyes them askew; and only by an absolute mastery of the mechanism controlled by temperament can the song be sung as Mozart heard it, so that the hearer may forget the box of cold keys and jingling wires. [Illustration: Mozart's ear. Common ear. MOZART'S EAR COMPARED WITH AVERAGE EAR. First published in Nissen's Biography of Mozart.]