The Siciliana of the
A Siciliana [or] Canzonetta is a brief song … Sicilian can-
zonettas are like gigues whose meter is almost always 12/8
Johann Gottfried Walther, Musicalisches Lexicon
(Leipzig: 1732), articles “Siciliana” and “Canzonetta”
The Siciliana lightens the serious tone that prevails in the other movements of the G-minor Sonata. Several factors contribute to this effect. First and foremost, it is the sole movement not in the tonic key of the sonata. It is in B♭ major, a key whose close affinity to G minor in a theoretical sense is enshrined in the term “relative major.” But hitherto in the G-minor Sonata, B♭ is an absent relative, totally missing from the Adagio and appearing only briefly in the Fuga—a reflection of the central role played by the subdominant in those movements.
In the other solo sonatas as well, the third movement is in a contrasting key: the relative C major in the A-minor Sonata and the subdominant F major in the C-major Sonata. By having a movement in a key different from that of the whole, the three solo sonatas differ from the solo partitas, in which all movements share the same tonic, imparting a single harmonic color to the entire series of movements.
This key change by itself imparts to the sonatas’ third movements a sense of relief from the tonal unity of the opening prelude-fugue pair. In the G-minor Sonata, this sense of tonal relief is strengthened because of the new key’s position in relation to the violin’s open strings. The two lowest open strings, G and D, permeate the sonority of the Adagio and Fuga: they are the bottom of the motto chord that opens and closes the Adagio and appear as the two pedal points in the Fuga. The tonic of the Siciliana may be only a minor third above the open G string; but with no crucial