Which scales for particular chords (ii-V-I )?

Question

Two part question:

1. If I'm playing a ii-V-I (e.g., Dm7, G7, CM7) and just want to improvise, what scales can I play with my right hand while on each chord, and why (so I can follow the logic and apply it to other chords in the future)?

2. According to the Circle of 5ths, I know I can play the major/minor scale of the major/minor counterpart. But aside from showing the major/minor counterpart, is the Circle of 5ths helpful for the previous question (i.e., figuring out which scales to play)?

Aside: It didn't sound very nice/cohesive when I played the D minor blues scale while on ii, the G major blues scale while on V, and the C major blues scale while on I. I feel like I'm doing something wrong.

Answer 1

If you play a ii-V-I in C major, all chords are taken from the key of C major, so in principle you can just play the C major scale over all three chords. Over the Dm7 chord this would be a D dorian scale, and over G7 it is a G mixolydian scale. But note that D dorian, G mixolydian, and C major all share the same notes; they're basically just the C major scale started on different roots.

Apart from chromatic passing and approach notes, which are always possible, you can add extra notes when playing over the V chord (G7). In jazz, it is common to add alterations to the V chord:

b9    Ab
#9    Bb (actually A#)
#11   C#
b13   Eb

You don't need to add all of them. You can try starting with the b9, which means that you'd still play G mixolydian over G7, but you exchange the note A for an Ab, which is usually resolved to the note G over Cmaj7.

A scale that has all altered notes is the G altered scale (7th mode of Ab melodic minor):

G Ab Bb B C# Eb F

So if you like you can switch from D dorian over Dm7 to G altered over G7 and back to C major over Cmaj7.

There are many other possible scales that can be played over G7 (e.g., whole tone, half-whole, phrygian dominant), but note that the way you resolve tension is at least as import as the exact notes that you choose over the V chord. As long as you resolve nicely, anything goes.

If you're not yet familiar with playing over a ii-V-I progression, I'd suggest that you mainly stick to the C major scale, concentrating on emphasizing chord tones over each of the three chords. Later on you can be more adventurous and use alterations and the scales I suggested above.

Concerning the second part of your question, I don't see how the circle of fifths will help you with improvising over a ii-V-I progression.

Answer 2

When you say scale, I hope you mean the notes from that scale rather than just running up and down. Playing Dm scale notes, either full minor or minor blues, usually works well over Dm. As does G major blues (or just G major, without the F#) over G, and the same with C. Actually, C minor blues and pents - maj. or min. work over C.

Since you mention ii - V - I, the I is telling. You could just stay within the C maj. scale notes. Dmin. will have the 'foreign' Bb, and G maj. the 'foreign' F#, both occurring in C blues. However, if you play CM7, the min. blues scale note will clash. Maybe for starters, you need to establish a change of chord by playing the root note on beat one, which puts the shape of the tune into perspective.