Playing scales over I IV V progression

Question

Playing over a diatonic I - IV - V progression in the key of C, one could use C Ionian over the I chord , F Lydian over the IV and G Mixolydian over the V. Of course these modes are just the notes of the C major scale. However, can one play the C major scale over I, the F major scale over IV, or the G major scale over V?

Is this ever used ? Does it work and why?

Also, can you combine... say going between playing the modes of the C major , and switching the major scales for the IV and V... also does it work and why?

Answer 1

TL;DR: Think in terms of chord tones, not scales.

You can, of course, play whatever you want. Digging deeper into your question, what you're really asking is: What can I play over these chords and have it sound good instead of sounding bad?

So in this spirit, I find the whole "you can play X scale over Y chord" approach to be the wrong way to think about improvisation. Thinking this way misses the point of the harmonic progression.

In the case of the C-F-G progression you mention, for example, you could play F—not the scale, mind you, just the note F—over the entire progression, and it would "fit the chords", in the sense that it's in the right scale for all three chords. But it would also sound terrible, because playing an F over a C chord is pretty dissonant (try it!). My point is that the whole "you can play any note from the C major scale over the C-F-G progression, and it'll sound good" approach is just plain wrong.

Instead, I encourage people to think in terms of the chord tones of the progression and to find ways to move from chord tone to chord tone. The chord tones—the 1, 3, and 5 of each chord in the progression—represent a kind of "connect the dots" game in which you try to move from a chord tone of one chord to a chord tone of the next one in an interesting and melodic way. In this metaphor, the dots (the chord tones) represent safe, reliable points of consonance off of which you can hang the rest of your solo.

As you become more comfortable thinking this way, you can experiment with expanding your concept of what the chord tones are to include 7ths, 9ths, and other extensions, effectively adding more dots you can connect. And you can experiment with drawing outside the dots—i.e. creating tension by playing non-chord tones, deliberately introducing dissonance—so long as you can control that tension and resolve it in a musically satisfying way.

Answer 2

First, you can play whatever you want whenever you want. The question is if it sounds good. That's not to say the theory isn't useful. Use the theory to help explain why something seems to work or not or as a jumping off point to try something new. But try it first to find what your ears tell you.

As for the theory here, yes you could just play a major scale from the root of those chords if they are just triads, but it gets more problematic using 7th chords. For example if by G major you were talking about a G7, the diatonic dominant 7th chord in the key of C, then you'd have an F# in a G major scale whereas the G7 chord has an F natural. That's not to say you couldn't play it but, in the theory sense, that's where major scale over the chord root idea starts to go wrong (C and F are fine because those are Maj7 chords diatonically in C).

It's also worth noting that any of these scales would sound mostly right over any of these chords because there's not much difference between them. The key of C has no sharps or flats, G has only 1 sharp and F has only 1 flat. So depending on how often you use the B vs. Bb or F vs. F#, it could be any of them. Speaking of which, if you take out all the B's and F's from the keys of C, F, and G, you get a 5-note scale. Does that sound familiar? Can you guess which one it is?

C Major Pentatonic

As for why it all works, do this any time you are unsure about a given chord/scale context:

1. Construct the chord and write the notes out
2. Write the notes out of the scale/mode that you're trying to use
3. Is there a lot of overlap? For instance if all the chord tones exist in the scale it would sound very "inside" or consonant. If there are lof of exceptions where the notes differ it will sound very "outside" or dissonant.

It's really that simple. There are a lot tricks like "oh you can play this particular scale over this type of chord" and those things are worth checking out. But all of those tricks work (or don't) to varying degrees because either the notes overlap or they don't.

Answer 3

Playing C Ionian, F Lydian and G Mixolydian, exactly the same notes are being used - C D E F G A and B. As you say, you are aware that this is the case. For guitarists, it may not be that obvious, as the pattern learnt for Mixolydian/Lydian/Ionian may not reveal the same notes - they are the same, but with a different pattern comes a different mindset. It wouldn't be the first time I've encountered this thinking!

However, the question. On an F bar (in key C), the F scale notes can be made to work; the only difference is Bb instead of B. It's going to depend where in the phrase it gets played. The same with G scale notes; F# in place of F, which actually gives the mode notes of C Lydian.

So, instead of thinking only modally, or only key scalarly (made that up!), use all the available notes. Now, the choice is from C D E F F# G A Bb B. In fact, a Bb over a G chord will work in that it makes a bluesy feel - what's wrong with that?

The more important factor is to use chord tones on the main beats, as, for example, when on G, a G B or D note on the first and/or third beat of a 4/4 bar will make it sound like it fits well.

When all that is coming more naturally, and there's less thinking involved, expand each chord. Like, on an F bar, use b7 as well, (no point mentioning the 9 or 11 or 13 as they're already available from the F scale!).

I've kept it straightforward here, but the ideas could (and jolly well are!) expanded every time someone extemporises in most styles - obviously jazz comes to mind, but I'm sure Bach, Listz et al used the same principles, too.

Bottom line is the usual 'if it sounds good, it probably is' - all of which can and will be explained in theory, but quite often players don't allow themselves to let theory lead - there are many good players out there who are ignorant of the theory, and it hasn't slowed them down.