Bach J.S. - Prelude in C BWV 939


J.S. Bach (1685-1750) needs no introduction. He wrote at least 20 little keyboard preludes, and this is one of a set of five collected by his pupil Kellner.

In the Baroque period the prelude was one of the most popular forms. It was often coupled with a fugue or fughetta, or given as the first movement of a suite, but could also stand alone.

Pupil Match & Suitability

This is a lovely gentle prelude requiring good legato touch and sensitive phrasing. The music quite often spans octaves so the student with very small hands could find it uncomfortable.

Style & Tempo

The style of this music recalls Bach the organist who also loved to play the clavichord – both instruments capable of a rounded and mellow sound, in contrast to the plucked attack of the harpsichord.

The piano can emulate the best of both possibilities – the flexible and expressive tone of the clavichord and the sustaining power of the organ. However, the timeless quality of this composition means there is no need to strive towards the sound of any particular instrument.

Phrasing & Articulation

The first eight notes, which provide the melodic material for the whole piece, provide a natural shape which a string or wind player would slightly phrase off, whilst bars 1-4 make up the main first phrase.

Similarly, there is a layering of different lengths of phrase as the piece goes on. In bars 4-7, short phrases overlap and flow directly into bar 8, where a longer phrase develops.

Although there may be no obvious phrase ends there are still plenty of little 'breath points'. These do not need great emphasis, which would sound mannered, but awareness of the shapes will prevent a rendition of just one quaver after another.

Tone & Texture

Dynamics are, of course, optional as in all music of this period before the piano. However, the expressive possibilities of the piano need not be suppressed – the clavichord had a continuous dynamic range, albeit from ppp to mp.

The opening octave needs to be played loudly enough to carry through 3 bars and the RH can either grow as it sets out the first phrase or die gently away to match the decay of the LH.

Echo effects can be tried in bars 4-8. Bars 9-11 lend themselves to a crescendo. If the student prefers to think in harpsichord terms, dynamics will be of the “step” variety, alternating between p/mp and f/mf. It is interesting to keep experimenting.


A real familiarity with chord shapes will develop as this piece is learned. There should be no sense of tension or effort in stretching for octaves. Over-holding should be avoided, as the broken chords often turn back on themselves and overheld notes could clog up the flow.

The LH mordents in bars 9-11 should sound (and indeed be) effortless. To achieve this they should be carefully practised slowly, with no more effort than needed to play the notes: check that the fingers are not being pulled up too high and that the arm is relaxed.


If the student's hand is big enough it is economical to finger the broken chords in sets of four rather than three notes (e.g. bar 1 RH C-1 E-2 G-3 and Bflat-5) so that the hand does not have to keep stretching out for the top note.

RH bar 13 fingering has implications for setting up the semiquaver run in the following bar: a larger hand may feel comfortable with 1, 2, 3, 5, 3, 2, 4 (on Bb) 3, 4 (on A) but this means the 4 needs to turn over the thumb for the second beat.

A more nimble fingering in bar 14 starts on 3, so the RH in bar 13 would be better off with 1, 2, 3, 5, 2 (on G) 1, 4 (on Bb).


The mordents in bar 9 should be continued into bars 10 and 11 if they are played at all: it would have been well understood in Bach's day that this was required.

However, if the student is struggling to play them even after careful practice, it is better to omit them altogether than spoil the flow and enjoyment of the piece.


There is no need to pedal this piece at all.

Teaching Strategies

This is an opportunity to introduce the student to the sounds of keyboard instruments that Bach would have had in mind as he composed:


Chamber organ

Together with the string music suggested previously, this should help to deter the student from playing mechanically.

Practice Tips

Identify and play the four-note chords which make up the first 3 bars of the RH, and look for similar groups elsewhere.

Play four notes as a block, stay on the chord whilst working out where the next group goes and then move straight there. This will aid fluency and help with understanding the phrasing.


In all the quaver broken chord passages, listening is vital to ensure there are no lumps and bumps as the hand changes position.

Students who do not bother to count may make unsuitable breaks which sound like hesitations in bars 4 and 8.

Conversely, students who over-use the metronome will not develop the required flexibility for phrasing the quavers. It is best to insist on a steady internalised pulse which can also be spoken aloud whilst playing.

Final Performance

An excellent performance will display real pleasure in the craftsmanship of this piece, with beautifully shaped phrases and a delicate variety of touch. Technically secure, played at a well-chosen and consistent tempo, there will be an authority that belies the brevity of the piece. Ornaments will be played with enjoyment and the semiquaver flourish at the end will have a pleasing rhetorical quality.

A good performance will have charm and ease, with phrase shapes clearly well considered. There will be a sense of period style and the ornaments will be played without fuss. Any slips will be reabsorbed into the flow. A sense of structure and purpose will keep any technical worries at bay and lift the basic performance out of the ordinary.

A sound performance will be plain and simple, at best enabling the music to speak for itself. It may sound a little stiff and repetitive. Some hesitations may crop up where hand repositioning is not quite secure and bar 14 may show signs of anxiety. Dynamics may be absent or minimal

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