Noctave
The piece
This prelude opens the first book of The Well-Tempered Clavier (1722). It develops a single gesture: each bar sounds one chord, spread out twice in the same pattern. Near the end, a long pedal point on G in the bass prepares the return to C, and a pedal on C brings the close. Charles Gounod later laid a melody over it, which became the so-called Bach-Gounod Ave Maria.
The right hand spreads three rising notes, twice per half-bar, while the left hand plays a bass note and then a second note a sixteenth later, both held. That offset is the delicate point: the left hand must press its second note without releasing the bass, and the right hand must start just after. With about 3.5 notes per second in the right hand at 66 beats per minute, evenness is everything. To learn to read these chords rather than single notes, note fading helps you move gradually from keyfall to the score, where each bar becomes one chord to recognise at a glance.