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Suppose we have a simple blues in E with the following chord progression

E7 A7 B7 E7

and that we have to play

Over E7: Em penta scale

Over A7: mix of A major and A minor penta scale

Over B7: B major penta scale

Does this imply that we are changing key chord by chord? In other words, how can we say that it is a blues in key of E if we are altering the melodic line each chord (although, due to its structure, the tendency of that progression is towards E chord)?

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  • One thing that can expand your soloing greatly: try also the E major pentatonic scale over the E7 chord. In major blues, both the major and minor scale work! It will definitely give you a different sound (think "before you accuse me" by E. Clapton as an example of a major blues sound) – mkorman Apr 27 at 13:53
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Improvising musicians often try to find a single scale that embraces all the chords in a sequence, and call that scale the 'key' of the sequence.

That can work. But other chords can also be used, ones that don't fit that one scale, and they don't necessarily mean the music changes key. Not even to the limited extent that a secondary dominant implies a temporary new tonal centre.

The home chord of a Blues in C is C7. That doesn't make it temporarily a Blues in F, and when the F7 chord comes along it doesn't make it temporarily a Blues in B♭.

You can duck out of the issue by playing a C pentatonic scale over the entire sequence. C7, F7 and G7 don't all fit a complete scale, but they fit half a scale - one with the 'problem' notes left out!

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No, it's not changing "key."

To really answer the question you would need to see the main melody of the song.

Typically the melody would be in a blues mode with a tonic of E. That will not be diatonic, like the key of E major. It's more chromatic. But that doesn't mean the tonic is changing during the song.

When you talk about "play this scale over that chord" it's some version of the "chord/scale system." That is more of a cheat sheet approach for what to improvise over a chord progression rather than a way to analyze the "key" of a song.

Another way to look at it with just the example you give is this. When you go through the progression...

E7 A7 B7 E7

...you start on E7 and then return to E7, E is your tonic. Whatever harmonic diversions you take going from E and returning to E do not change the fact that E is the tonic, the "home."

Actually, you want to embrace this idea of an E tonic in an improv. You want to move through the A and B to get to an ending on E. If you treat A and B like new keys, as new tonics, homes, points of focus (however you want to think of it) the melodic line will probably not flow well. You might end up with 4 disjointed bits instead of one connected line in E, E blues.

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  • Thanks Michael. I try to be more specific: the fact that the central tone of the melody is not always E but in A7 it becomes A because I play some lick in A (major or minor penta), and in B7 it becomes B for the same reason, doesn't this imply a continuous translation of the key? – LeoAn Apr 27 at 13:44
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    @LeoAn it doesn't (imply a continuous translation of key). Think of it as buildin tension... the solo builds tension as it move to A, even more as it moves to B, and then it's released when it goes back to E. The issue here is, as Michael has said, that blues is non-diatonic. That is, to play blues properly, you have to add a lot of accidentals, so you're not sticking purely to the 7 notes of a given key (E in this case). These accidentals are what give the song (your solo!) a bluesy feel. – mkorman Apr 27 at 13:52
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    @LeoAn, I understood this is what you are doing, and it may create a feeling of change key with each chord, but my point is this isn't the typical way to play blues. You're applying a "chord/scale system" notion in the wrong way for blues. A typical thing might be a basic E blues lick, repeated over all the chord changes, the resulting "clash" of tones is embraced as part of the essential sound of the blues. – Michael Curtis Apr 27 at 14:28
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    Staying with the E blues scale, or an E major scale embellished with blue notes, for the whole chord progression is the typical way. The concern is to then develop the improv more rhythmically. When you focus on pitches to match the changing chords, the focus becomes more harmonic (the line weaves in and out of chord tones) which is more like jazz. – Michael Curtis Apr 27 at 14:35
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    Look at the lead sheet heads for blues like C Jam Blues, Cool Blues, or Bag's Groove, basically the simple lick stays the same over the changes, the melodic tones alternately "fit" or "clash" with the chords. Or, if you want to view it in chord tone terms, tones that are chord tones over one chord become non chord tones in different chord, but like wise other tones then become tones of resolution. But that harmonic thinking becomes tedious in the blues. Don't worry about the clashing, just focus on the "targets", the end of phrases resolving. – Michael Curtis Apr 27 at 14:51
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Playing a Blues with E7, A7 and B7 means you're definitely in key E. when the progression moves to A7, and then B7, you're still in key E.Imagine a song with half a dozen chords in it. Every time the chord changes, we change key? No, no, no!

Using Em pent over E7 works well. There are plenty of players that use Em pent. over A7 and B7 too. It sort of works, but the problem is, some of the notes become avoid notes over the other chords.

When you check out the actual notes for each of the three, you'll find they're pretty close to each other - there's a small change involved between each, but with a different 'home' note, mainly.

And why should we have to play the various maj/min pents over those specified chords? Both maj. and min. pents work over all three, and that's what most good players use! Give it a try, and expand your lead playing exponentially!

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  • Thanks Tim. "It sort of works, but the problem is, some of the notes become avoid notes over the other chords": which are the notes to avoid? Analyzing the tones inside each chord, Em penta should work well in A7, of course it works on E7, I have more doubt in B7 chord, in particular with regard to G and D notes. – LeoAn Apr 27 at 13:30
  • Using ears is the answer! The D works over B7 as much as the G works over E7. – Tim Apr 27 at 13:33
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Most other answers say no, and I do agree - mainly because 'key' is a word usually used to describe the tonality of whole pieces or sections larger than the duration of a single chord....

...but if you really feel you are changing the scale you are playing on every chord, there is a good chance that doing so may give some sense of 'tonicisation' to each chord. This can make each chord change sound like a bigger, more dramatic motion. You might find yourself leaning towards this feeling if you base your playing around riffs that you transpose to the root of each chord.

What's the difference between a temporary tonicization and a modulation to a new key? Someone more knowledgeable might be able to give an answer in terms of whether you encounter certain cadences or something like that, but to some extent it's just that a modulation is a larger scale 'feature' of a piece.

So while it would be unusual to talk about a blues chord change as a key change, for some pieces, it might be interesting to try thinking of it like that and see where that takes you.

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In key changes, the most important factor is the tonic - does it move. In this simple blues chord progression, I don't feel tonic movement away from E. And I doubt that you could play any kind of licks that would move the tonic, whatever solo notes you layer over the backing chords. E is the home note. Well, as long as the backing chords change at a relatively reasonable speed. If each chord lasts for two minutes, that's different.

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