Scales or arpeggios?

[Jean-Michel G]

Warning: long post ahead! 😉

For blues and rock guitarists, the standard go-to approach for improvisation is the minor pentatonic scale. Brian recently said that you probably don’t need to know anything else in order to be able to improvise over a standard twelve bar blues, and I fully agree with him.

But Brian himself often also explains and demonstrates other improvisation approaches…
There are essentially two main approaches to improvise over a given chord progression (even over a blues):
1. One approach is to think in terms of scales
2. The other approach is to think in terms of chords

The question is whether there is a way to decide which approach to use and when.
And the answer, I believe, is yes.
There is no need to be super scientific about this, but still this is something I wish I had been taught much earlier and so I decided to share it. I hope you’ll find it useful.

In order to pick the best strategy to improvise over a given chord grid, there are two main parameters that you need to consider.

The first parameter is called the “harmonic rhythm”.
The harmonic rhythm is the speed at which the chords change during the song. It is of course somewhat dependent on the tempo, but yet different. Two or more chord changes per bar would be considered a fast harmonic rhythm, even for relatively slow tempos. On the other hand, chords lasting for two or more bars would result in a slow(er) harmonic rhythm, even at fast tempos. At one chord per bar, the tempo of the song will probably play a decisive role.

The second parameter is what I call the harmonic “pureness” (for lack of a better word)
Every key has its associated chords set, called the “diatonic chords”. The diatonic chords are simply the chords you can build on each degree of the scale for the given key, using only notes of that scale.
If the chord progression of a song only contains diatonic chords, it is tonally totally “pure”. But very often the progression also contains non-diatonic chords; for example in:
|G |Em |A7 |D7
the A7 chord doesn’t belong to the key of G and as such it “warps” or “bends” the harmony. The more such foreign chords, the more “warped” the harmony.

So, we have two parameters and two possible strategies; that’s four cases to consider.

First case:
The harmonic rhythm is fast and the harmony is warped.
In this situation, the best strategy is to use arpeggios. In doing so you will follow the changes without mistakes since you mostly play chord tones.
Of course, this is technically challenging at fast tempos…

Second case:
The harmonic rhythm is fast but the harmony is pure.
In this case, you will probably want to play nice melodic phrases using the scale corresponding to the key of the song, without trying to follow the changes.
This will usually work well because possible “wrong” notes will resolve quickly with the next chords.

Third case:
The harmonic rhythm is slow and the harmony is warped.
An example is the famous tune “So What” from Miles Davis, in which the chords last forever and have nothing to do with each other.
In this case, a good strategy is to use scales corresponding to the underlying chords.
Here again you follow the changes, but with scales rather than with arpeggios. You could use arpeggios but they would probably become a bit boring.

Fourth case:
The harmonic rhythm is slow and the harmony is pure.
In this case, both approaches will work. Do what you want (or what you can!).

Often one strategy will fit one part of the song and another strategy will be needed for another part since the harmonic rhythm as well as the harmonic pureness may change during the song.

Of course, at the end of the day the two approaches converge. If you have a Dm7 chord in the context of a song in F major, and you play the corresponding arpeggio (D F A C), you are already playing four notes out of the F major scale!
This super long post is only meant to help you decide if you will try to follow the changes or not.

[JohnStrat]

Thanks for making this very knowledgeable post. You have put the information concisely and clearly in my view but knowing it will take a lot of learning at least for me.
Well done and thanks for taking the time to write this up.
Johnstrat

[sunjamr]

And don’t forget to use your ears! If it sounds good, it is good.

Sunjamr Steve

[Jean-Michel G]

I realized that the information contained in the original post above could easily be summarized in a table, so I just created one. See attachment.
Hope this helps!

[Author]

Posts