Bach 7 – The nature of Harmony


Without Music, we could completely destroy the structure of the space time continuum!

– Dr Emmett, Back to the Future


CHAPTER AIM: To look at the whole movement in terms of musical key





The Whole Piece

Brandenburg No 2 1st movement   

When we read a book, we have constant markers and delineators that tell us where we are. Chapter headings, page numbers, paragraphs, sentences, even the individual words themselves give us clear signposts about where we are.

J.S.A piece of music on the other hand seems to be a different creature. It flows continuous, beginning to end. Which is how, until the recent age of recording, the listener had to receive it. In one straight go, without pause.

Only that’s not entirely true. Music also has pauses, joins, places where a section ends and another begins.

The term for these are cadences. And although this music might seem like a continous stream, it does indeed have cadences.

The first comes just 20 seconds into the piece, where for a brief moment the music appears to ‘land’, before immediately springing back into action.

If we listen carefully there are in fact seven of these cadences. Here they are:

Whole Track  

  • 00.20    We land at the end of our first ‘section
  • 01.12     Another ‘landing’.
  • 01.41     Again, like the end of a chapter…
  • 02.34     Cadence no 4
  • 03.38     Cadence no 5
  • 04.29     Cadence no 6
  • 05.13     Final Cadence, and end of piece


Now if we use a harmonic lens to examine these cadences, we find something rather interesting. Each cadence seems to land in a new and different key, with the exception of the final cadence, which as we already know is a return to F major.

Let’s just look at the actual keys we finish in…

Whole Track   

  • 00.20    F major
  • 01.12     C major
  • 01.41     D minor
  • 02.34    Bb Major
  • 03.38     G minor
  • 04.29     A minor
  • 05.13     Final Cadence, back to F major




Key Approach


Whole Track


This may seems like rather a large number of key changes, but in fact this is rather straightforward, harmonically. In fact it’s as straightforward as you can get, as any guitarist would tell you.

It’s the I-IV-V progression common to most pop a rock music still. Our principal key is F major. The two closest relationships to our root notes are the V Dominant and IV Subdominant. Which in this case is Bb and C.


Next, each key also has its own relative minor. In F major, the relative minor is Dm.

If you think about how our two sets of melodic material are presented, they are introduced in F major (from the start) and relative minor Dm (01.19) respectively.

Bb and C have their own relative minors to, with G minor and A minor.


So in total we have F major, together with it’s 5 closest musical keys, Bb and C major, and the three related minor keys, Dm Gm and Am.


Let’s just go through the movement again,with a bit more description…

Whole Track

  • 00.00   F major. Tonic, or home key.
  • 00.36   C major. That jump up to the dominant of F brightens the sound.
  • 01.14   We briefly return to F major
  • 01.19   Now D minor, which is relative minor to F major. Darker tone from minor key
  • 01.48   Harmonic development. We are travelling, exploring.
  • 02.25   We move to Bb major, subdominant of F, again a very close relation
  • 02.42   Again, we enter a development section.
  • 03.15   Now G minor. Relative minor to Bb.
  • 03.50   That deft shift to D minor.
  • 04.06   Another deft shift into A minor, relative to C major, to complete our set of six keys
  • 04.30   Back to F major, with a bit more exploration, through to the end.


The three major keys (F,Bb,C) together with their relative minors (Dm, Gm, Am) make up a close family gathering.

But this harmonic set is really like an outer skin containing a more complex piece of design.

If we look closer at a section, we see the harmonic intricacy in more detail…


A Closer Listen

This section of the music appeared in an earlier quiz. It comes right up near the end of the movement, and comes with a number of fast shifts in key, or modulations. Here it is.

4.40  Key change section near end   

  • 00.00   This is Bb. But supported by a deep Ab in the bass.
  • 00.03   We move to G major. Much more distant to Bb.
  • 00.05   And now C, but again supported underneath a tone lower by Bb
  • 00.08   A major. Again, an exploratory leap.
  • 00.11   D major, but with C in the bass
  • 00.13   G major, perhaps, but harmonically unstable.
  • 00.16   And now we land on C major. Before…
  • 00.21   Back home, we’re coming back home in F major.


There’s alot going on in those few seconds. Those three chords anchored with lower bass notes at 0.00, 0.05 and 0.11. Not to mention harmonically even more ambiguous areas such as in 0.13.


But what this all does is set us up for our leap onto that final C major at 0.16, where for the first time in this section that we land on harmonically secure ground. And we can feel it. This is emphasized by the trumpet leading an orchestra playing together.

It all sets up perfectly that final leap up to F major (0.21) so set up the end.


It’s an surprising digression to put in so close to the end of the piece. But as always with Bach, the execution is effortless, and he makes the complex appear simple and natural. Which typifies Bach’s music. From a distance, firmly structured, from closer up richly decorated and adorned, sometimes in the minutest detail.


For a personal afterword on this genius, check the link below. Otherwise: onto another genius: Mozart!….





  • The topic of the tuning convention known as Equal Temperament is far more interesting than it sounds, and this documentary by Howard Goodall is a great watch. The subject of ‘just’ or ‘true’ temperament, as against equal temperament, creates a lot of heat to this day (much of it hot air) but I think it’s fair to say Goodall gets the essentials right.
  • This shorter youtube video runs over some of the principals of harmonics.