Prelude 13 in F-sharp major BWV 858

Book I of the Well-Tempered Clavier. Under its figuration, this prelude is 49 chord changes across 30 bars — ranked 27 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 13 in F-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 vi7 (F#) · vi7 (A#) · ii7 (F#) · V7 · #iv (F#) · II · vi7 (A#) · vii7 (B#) — and the whole prelude keeps moving at roughly that harmonic pace.

What it leans on

Of 49 labeled changes, the harmonies that do the most work: V7 (5×), vi7 (A#) (3×), IV7 (A#) (3×), vi7 (F#) (2×), ii7 (F#) (2×).

Free scores

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