Video — Bach Prelude XXI in B Flat Major

Here is my interpretation of JS Bach’s Prelude no.21 in Bb major, and you can find more information below the video.

When I sit down with Bach’s Prelude XXI in B-flat major, I’m reminded why his music never gets old, and has inspired so many composers that followed (including pop and contemporary styles). This is one of those pieces that feels almost as though it is pouring straight out of him in real time — so much so that part of the performance direction is quasi improvisando (almost as if improvised). That instruction tells us a lot about the kind of freedom of expression and interpretation that the great composers often advocated. Classical music (Baroque, Classical and Romantic) wasn’t (and isn’t) all about stiff formality as some prevailing stereotypes often suggest.

It is known that Bach (like many of the great Baroque, Classical and Romantic composers) was a phenomenal improviser.  And when playing this Prelude at tempo, with its endless stream of semiquavers and changes in tempo, that undercurrent of spontaneity makes itself known. It gives the impression of music unfolding freely, yet with perfect balance and design. Even though this piece of music is obviously notated, a lot of the great composers were known to be able to create structured and coherent extemporaneous compositions (i.e. composing in real time, improvising). This piece is just reflecting that tradition.

Why This Prelude Feels Like Improvisation

The texture of this composition is light, fluid, and full of momentum, and that combination lends itself to a freer sound. It doesn’t announce itself with grandeur or formality, and spontaneous sounding flourishes (often added freely and in different ways by different performers) decorate the melody. That flow and decoration is part of what makes it feel improvised, along with the tempo changes that really feel conversational.

For me, as someone who spends a lot of time improvising, this feels very similar. In my blues improvisations, I’m used to balancing structure (the 12-bar cycle) with freedom (what melodies and textures I create within those bars). In my modal improvisations I have used more freeform ideas, but still with an awareness of which chords are diatonic to the key, which provides some structure. Bach is doing something similar: the harmony is clear and predictable, but the lines themselves float and breathe with expressive freedom. This counters the stereotype of classical music (Baroque, Classical with a big “C” and Romantic) being uptight and lacking freedom.
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And this is why I think students and pianists of all levels can learn something vital from it: improvisation isn’t just “making things up.” It’s about playing with balance, between freedom and form, and really feeling the music. Bach teaches this lesson inside a notated score such as this piece.

The Technical Challenge

This Prelude is very technically demanding, and when practising it, can really help develop your technique. When brought up to speed it requires:

• Finger independence.
• Even tone across long runs, but not so even it sounds mechanical – strategic accentuation helps shape the runs.
• Control at velocity — avoiding rushing or blurring, whilst still putting in enough flexibility to avoid sounding mechanical.
• Mental stamina — staying focused through very long runs of semiquavers.
• Relaxed wrist — otherwise you lose that control. It can be very hard to avoid excessive tension at this sort of speed.

This kind of piece builds a kind of discipline you can’t always get from mechanical drills alone.

Why Fast Bach Preludes Are “Secret Exercises”

Many pianists spend hours with Hanon or Czerny exercises — and those are definitely infinitely valuable (just ask some of my adult students how often I prescribe Czerny studies!). But Bach’s preludes give you some similar technical benefits, in combination with the potential for development of great depth of expression.

Take this Prelude as an example:    

• You’re training your fingers.
• But you’re also training your ear — to shape phrases, to make the melodies breathe within the music.
• And you’re training your musicality — learning to create flow and expression, not just accuracy. Playing a piece of music isn’t just about playing the correct notes with the correct rhythm.

A Pianist’s Reflection

Playing this piece has similarities to improvisation. Once the notes are learned and ingrained in the muscle memory, you are free to simply be inside the sound. Free to feel rather than think; and to incorporate your own dynamics, embellishments and rubato as part of the interpretation. That’s very valuable and can really go a long way towards developing general musicianship.
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Improvisation and interpretation aren’t opposites. They’re complementary musical skills. Both are about entering a flow state where music feels alive in the moment. Spontaneity and structure can co-exist.

My Interpretive Philosophy

For me, the heart of Bach lies in clarity, sparkle, and rhythmic vitality. When I was a teenager, I had the best piano teacher anyone could ask for, and he encouraged me to play with a leggiero, almost non-legato touch, which brought out the clarity and independence of voices and the lightness and effervescence of the texture. Later on, another teacher urged me toward a heavier, Romantic-style legato, but I found that approach blurred the textures and weighed the music down, particularly in Baroque music.

I’ve held onto that early training because it reflects how Bach would have been heard on instruments of his time: expressive through articulation rather than pedal, buoyant rather than over-sustained. To my ear, this brings out not only the contrapuntal intricacy but also the sheer freshness of the writing. This sparkle and delicacy also works incredibly well in Mozart’s piano music, and many other styles too, including Romantic music at times. For me, interpretation is about making choices that let the essence of the music breathe. And we all have a right to inject some aspect of our own personalities into the music, which can be what brings it to life.