Prelude 4 in C-sharp minor BWV 849

Book I of the Well-Tempered Clavier. Under its figuration, this prelude is 44 chord changes across 39 bars — ranked 20 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 4 in C-sharp minor, reduced to labeled block chords — The opening, reduced: one block chord per change, functional labels above.

How it opens

The first changes are VI7 (C#) · V7 (B#) · V7 · VI7 (G#) · iiø7 (F#) · v7 (F#) · i7 (E) · iv7 (E) — and the whole prelude keeps moving at roughly that harmonic pace.

What it leans on

Of 44 labeled changes, the harmonies that do the most work: V7 (D#) (4×), VI7 (C#) (3×), V7 (3×), VI7 (G#) (3×), v7 (F#) (3×).

Free scores

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