Bach’s Invention No. 13

When I was a young guitar player I really loved the stuff by JS Bach and others, but I was very intimidated by the whole thing. I didn’t understand how it all worked and there were so many sharps and flats at various points. I had no idea how it all worked!

Hopefully we can clear up some confusion. Bach’s two-part inventions are a great way to start understanding chord progressions so we can improvise in this style. This is pretty hard to play on guitar as it was written for piano (2 hands) but we can at least analyze it and simplify it for our purposes. Here’s the sheet music:
Bach Invention 13 a4

Inventions have some neat features. You’ll notice that lines in the right hand (upper part) are repeated in the left hand (lower part). And the lines are ‘developed’ or twisted so you’ll notice the same line in other spots maybe higher or lower (different notes but same idea). The line can be inverted (goes up instead of down, intervals are inverted), slowed down (eighth notes instead of sixteenths), transposed (moved up the scale or into another key) and more. Also when one line is busy with sixteenths the other is usually eighths, so you have a question and answer type approach and it makes the busier line stand out if the other isn’t quite as busy.

Another thing to note is that the bass isn’t always playing the root of the chord. Sometimes it will be the 3rd or the fifth. This can bring variety to a simple chord progression and make it sound different.

First thing we look at is the key signature. Notice no sharps or flats so most likely we’re either in C major or A minor. On beat one we have an A in the bass and C, E, A in the upper register. This spells an A minor triad then we have on beat 2, G# in bass and B, E and D so we’re looking at an E7. Beat 3 we have A, E, C in bass and C, E in upper register so looks like Am again. Beat 4 we’re back to E again. So it’s looking like we’re in the key of Am and going back and forth to the V chord (E or E7). Remember that in minor keys the V is often major instead of the expected minor (by raising the 7th degree of Am which is G#).

Here’s the rest of the analysis and how to use it in your improvisations:

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