Learning Piano Improv — Tip No. 1: Shadow Pentatonics

Level: Intermediate to Advanced

Each sequence of notes you play on the piano — whether it be a scale, an arpeggio or some other sequence — has what I call a “shadow”. The shadow of a given scale is that sequence of notes that aren’t included in the scale.

To keep it simple, I’ll concentrate on major scales here, but you can extend what I say to any scale, arpeggio or other sequence of notes that you’re trying to learn or use as the basis for improvisation. Let’s look at an example to get the idea.

The C major scale contains seven different notes: C, D, E, F, G, A, B — all the white notes on the piano. This means that there are five notes that aren’t included in the scale: Db, Eb, Gb, Ab and Bb — all the black notes. (You can call these same notes C#, D#, F#, G# and A# if you like, but I find it easier to think in terms of flats rather than sharps.) These notes comprise what I call the “shadow” of the C major scale.

Look carefully at these five notes. If we play them in ascending order, starting on G — hey presto, we have the Gb pentatonic scale! So the shadow of the C major scale is the Gb pentatonic scale.

Given that every major scale contains exactly the same sequence of interval patterns as the C major scale, we now know that every major scale has a shadow pentatonic scale.

A quick way to remember which pentatonic is the shadow of which major scale it to note that in the key of C, the shadow pentatonic is constructed on the note that’s a tritone away from the tonic of that key. The interval of a tritone is sometimes called an augmented fourth, or a diminished fifth, and you can find it by counting up or down three whole tones (or six half tones) from the starting note. So it sits exactly half way between a given note and its octave.

Why should we be interested in the shadow pentatonic of a major scale? I can think of a few reasons, but I’ll just give a couple for now (I’ll add more later, if you’re interested):

1.         It gives us an easy and quick way to learn, memorise and visualise which notes belong to a given major scale, and which notes are not included in that scale. One of the reasons most piano teachers start teaching students music in the key of C is because there’s a powerful visual reminder of which notes your fingers have to find: all the white notes. But once you start learning to play in keys that contain a mixture of black and white keys, you don’t have this easy visual cue to help you to learn the scale, to avoid wrong notes in the scale, or to improvise within that scale. However, if you learn each scale alongside its shadow pentatonic, and try to visualise the notes of the shadow pentatonic as “avoid” notes for that scale, you’ll find it helps you to improvise freely in the key of the scale much more quickly.

2.         It gives you a way of remembering the “alteration” notes of the scale — for example, the notes that turn the C major scale into the mixolydian mode (Bb replaces B natural), or the dorian mode (Bb and Eb replace B and E natural), etc. You can devise your own way of learning these alteration tones, but one way is to memorise the order in which the notes of the shadow pentatonic  scale enter the original major key as alterations, as you create the various modes that have the same keynote as the major scale. The following sequence, starting with the C major scale (also known as the ionian mode), might help:

To create C mixolydian, add step 3 of the shadow pentatonic (Bb instead of B natural) to the ionian mode.
To create C dorian, add step 5 of the shadow pentatonic (Eb) to the mixolydian mode.
To create C aeolian, add step 2 of the shadow pentatonic (Ab) to the dorian mode.
To create C phrygian, add step 4 of the shadow pentatonic (Db) to the aeolian mode.
To create C locrian, add step 1 of the shadow pentatonic (Gb) to the phrygian mode.

I haven’t given all the details of which note gets left out to make room for each alteration, but I hope it’s obvious that it’s always the note that has the same name (A, B, etc.) as the new, flatted note (Ab, Bb, etc.).

The one remaining mode we haven’t created in this sequence, by adding one alteration after another from the shadow pentatonic, is the lydian mode. To create C lydian, we need to go back to the C major scale (ionian mode) and add just step 1 of the shadow pentatonic (Gb) to that scale/mode — except that we now call it F# rather than Gb, because the note we’re altering this time is F, not G. There are complex theoretical reasons why the lydian mode seems to be a bit “different” from the others in relation to the sequence of modes I’ve outlined here, but I think there are ways of bringing this “black sheep” back into the fold in a fairly neat way. But I’ll leave that for another day when we all feel ready for some more serious music theory.

So, for the most immediate purposes, if you haven’t yet learned all your major scales and all your major pentatonic scales, then you’re in luck. You now have a very effective tool to help you to learn both sets of scales quickly and easily — and, more importantly, you have a way of relating them to each other that can get you improvising more quickly, and you’ll understand more of what you’re doing and why it sounds a certain way!

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