Bach C Major Prelude: Analyzed and Performed

Some years ago, during some time was available for more interesting side projects, I built some tools to analyze Music Notation. It wasn’t to analyze patterns in the sounds you hear with Music, but the symbols people use to read Music. Having graduated from one of the world’s best Music institutions, I know a thing or two about having to read Music from 1500-Today.

In this article, we look at Bach’s C Major Prelude from the Well-Tempered Clavier, Book 1 — BWV 846. The focus is ultimately to find new ways of studying Music. A few different products were created, and the one that is discussed here is the Curtis Card. It is a custom CLI tool I built to perform map/reduce functions on the dataset presented from Music in a Lead Sheet form.

It cannot be understated that Music, the visual language is an interpreted language. This means that while there is a structure to the compositions, via the visual elements (grand staff, bar lines, note heads, rests, etc), how a performance is executed in real-time is left to the reader to understand and implement as they see fit. Because of this, two uniquely different interpretations are presented of this piece to demonstrate.

You can find the full sheet music on the International Music Score Library Project (IMSLP):

IMSLP Link — JS Bach C Major Prelude

To start, you can listen to this piece performed on a real (non-sampled) piano.

While you are listening, let’s look at Sheet Music. Here is a snippet from the score with Chord Symbols assigned. The chord symbols are key here, as they denote the vertical harmonic structures that will be present when all the sounds sound together. Depending on when the Music was written, the assignment of Chord Symbols can be either really easy (Jazz Standards were mostly written around Chord Symbols) or really difficult (Classical Music from eras where Chord Symbols were not used).

In perhaps one of Bach’s most famous and influential pieces, we find patterns that are present in Jazz (1900–1950) are also found in pieces written hundreds of years earlier, with this one written around 1722. Easily 200 years, and continents away, we find that these patterns are in a way universal. By and large, this has to do with how Sound Acoustics work and is not the point of this article to discuss.

After chord symbols have been assigned to all measures in the piece, it was run through the Curtis Card algorithms to see if any patterns that were found in Jazz pieces might be found in this simple piece by Bach. Here is the full prelude in the Lead Sheet format.

There may be alternative ways to analyze this piece, but this is how it was marked up. This includes all the patterns it found in the form of the Music as it is notated.

The first 11 measures of the Curtis Card are presented here to demonstrate how the assignments were created.

Curtis Card Analysis

The first thing that stands out is the fact that it found multiple 2–5 and 2–5–1 relationship in the first 11 bars. This is not discussing modulation or harmonic function assignment, just relationships. A 2–5–1 or 5–1 Pattern is so commonly found in Music, it is important to understand when they occur, as they signal resolution in sound patterns.

The other important information that is found is that the algorithms have assigned harmonic function to every single note in the piece. This is what you see: 1 C 3 E 5 G 1 C 3 E

C Maj — Root 1: C … 3rd: E … 5th: G

(1) [C] … (3) [E] … (5) [G] … (1) [C] … (3) [E]

(the note in relationship to the fundamental chord symbol) [Sounding Note]


D Min 7 — Root 1: D … b3rd: F … 5th: A … b7th: C

(b7) [C] … (1) [D] … (5) [A] … (1) [D] … (b3) [F]

(the note in relationship to the fundamental chord symbol) [Sounding Note]

That was the intention of the systems and tools that were developed, to data-mine Music in an effort to do complex pattern analysis.

Are their applications to this kind of research? As a composer, performer, student, and life long learner of Music, I totally believe so. It can streamline the process of learning new pieces, understanding existing pieces, and help with teaching improvisation. There are plenty of use cases, and hopefully, they can be explored further in the future.

If you are interested in learning more about complex notation analysis, please reach out! This work can no longer be done in a vacuum.

To close this out, here is an alternative recording of the Prelude on a real (non-sampled) piano:

A Data Wizard

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