For the first few Preludes of his cycle at least, Chopin follows a pattern where ordered pieces in the major keys alternate with chaotic and harmonically unstable explorations of the minor keys. By the way, if you haven’t read them, I suggest you check out my analysis of the first and the second preludes. This contrast between simple major and complex minor will be something that we will follow throughout the entire work, although the composer wisely puts in some interesting exceptions to break up the monotony that a strict alternation would create. We will explore these in due time, of course. Meanwhile, let’s take a look at prelude No. 3, which is probably the simplest and the clearest of the whole series, except for the classic No. 7 in A major:
The form and the harmonic structure being self-explanatory for the most part, the piece does not need further reduction or formal schemas. It is a standard period, framed by a 2-bar introduction and a 6-bars coda, both simply establishing the tonic G chord. The period has a slightly asymmetric antecedent at 9 bars (4 bars presentation + 5 bars continuation) which leads to a half cadence on V. The consequent starts with the same 4 bars presentation, but moves towards a long tonicization of the sub-dominant which stretches the continuation to 12 bars, for a total duration of 16 bars for the consequent.
In terms of texture, the piece is really a study for the left hand of the piano, which is consistently very fast, contrasting with a (proportionally) slow right-hand melody which has a brilliant polonaise style. Somewhat surprisingly, the left-hand pattern never changes except in bar 24 to accommodate the partial cadential 6/4 appoggiatura. Usually, arpeggiated accompaniment patterns are treated as a multiple-part harmonic structure, which follows at least loosely voice-leading rules; but here, the pattern is simply perfectly transposed up and down, all chords being in root position and creating virtual parallel fifths and octaves. The reason is probably pianistic: the predominantly white-key tonality lends itself less to stretching extremely fast runs than black-key equivalents. Or maybe Chopin liked the contrast between a blocky left-hand and a very fluid right hand.
After this break in harmonic complexity, we will have quite the opposite in the next prelude, which features some of the most chromatic harmony of the whole cycle.