Prelude 3 in C-sharp major BWV 848

Book I of the Well-Tempered Clavier. Under its figuration, this prelude is 104 chord changes across 104 bars — ranked 23 of 42 by measured difficulty (advanced) in this survey. Played as block chords, it's a progression you can learn in an afternoon; the piece is that progression wearing sixteenth notes.

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Opening bars of Prelude 3 in C-sharp major, reduced to labeled block chords — The opening, reduced: one block chord per change, functional labels above.

How it opens

The first changes are I · ii · I (E#) · IV · I (E#) · viio (D#) · I · vi7 (G#) — and the whole prelude keeps moving at roughly that harmonic pace.

What it leans on

Of 104 labeled changes, the harmonies that do the most work: V7 (11×), I (G#) (10×), I (6×), ii (5×), I (E#) (5×).

Free scores

Blocked-chord reduction (MusicXML) — the harmony skeleton the player performs
The prelude as written (MusicXML)