The opening of Mozart’s quartet in E-flat, K.428 gives us really good opportunity to examine the composer’s use of chromaticism. What’s chromaticism? Well, an ordinary (diatonic) scale — as in Ex. 2 below (of C major) — uses only 7 of the available 12 notes between one octave and the next, whereas the chromatic scale gets to use all twelve of them (Ex. 1). Mozart’s use of chromatics was to be a significant influence on subsequent generations of composers, culminating in such works as Tristan and Isolde and Verklärte Nacht and leading, eventually, to Schönberg’s twelve note system.
A list of all 23 Mozart quartets plus some other useful bits and pieces:
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