Lydian fourth degree and system of differences: The example of the Symphony in A minor, op. 63

Abstract

The tritone plays a key role in the Symphony in A minor. Since the medieval
theory of the octoechos, the tritone occupied a specific position among the other
intervals. Within the tonal system, it remains the main dissonant interval, both
“destructive” of tonality as carrier of instability and tension, and carrier of the tonal
affirmation in the dominant chord. Sibelius, however, utilizes it in a mobile way
that blurs tonality. When the tritone is built upon the tonic, only the ascending
leading tone finds resolution on the fifth, while the tonic itself resists the
descending attraction. The first theme of the Symphony op. 63, presenting from the
outset the interval of the augmented fourth as the key interval, imparts the aesthetic
power of the whole work. One finds it therefore as characteristic element of the
initial theme of both the second and the last movements. The Fourth symphony so
gains a unique position in the production of the composer: Sibelius, with this
singular work, goes largely beyond the mere role of Finnish composer among the
European composers of the first half of the 20th century.