At times, I find myself getting impatient with the tyranny of half and whole steps. When I listen to most jazz guitarists' work (definitely including my own), it seems to me that we play it safe too often. There tends to be a lot of scalar motion, most of it well inside the changes. Very predictable.On the other hand, I find most lines based on wide-interval motion (fourths, fifths, etc.) to be somewhat artificial sounding and academic - too much like a hip trick that gets dropped into a solo somewhere. ("Check it out - I'm playing in sevenths! Technically impressive, no?")
When I'm craving a little something different, I'll often go for a chord-on-chord approach. This is sometimes referred to as superimposition, usually by someone who wants to impress you. To keep the BS to a minimum, let me explain it simply: all we're doing is thinking of one chord while playing over another chord. If we're looking for wider intervals without a lot of dissonance, we'll use a chord that's closely related to the one we're playing over. If tension is what's called for, we'll use a chord that's not so closely related. If we play mostly chord tones, we'll get built-in wider intervals in the line, since chord voicings tend to contain lots of thirds and fourths, etc.
In Example 1, I'm playing over a ii - V progression in the key of C. Over the Dm7 chord, I'm playing chord tones from Em and Am. These are both chords contained in the C major scale (or D dorian mode, if you'd rather look at it that way). Over the G7alt chord, I'm playing tones from Db and Eb major chords; these triads live within the G altered dominant scale (the dreaded G "superlocrian mode"). The last phrase is somewhat ambiguous; I was basically thinking of E minor and B minor. The F# in B minor gives this phrase a Lydian (major with #11) flavor. To the purists in the crowd: sorry about the final right-hand tap; I realize this marks me as a minion of pop commercialism. Sometimes I even bend strings.
Play Example 1
Example 2 happens over a ii - V in D minor. Over Em7b5, I'm thinking G minor. Over A7alt, I used the tritone sub principle and played Eb13. On D minor, I played an Aadd9 chord, waiting till the end of the line to resolve to the third of D minor. You could think of this as coming from either the D dorian mode or the D melodic minor scale; I didn't play a 7th from either scale, so it doesn't matter.
Play Example 2
I'd like to make a couple of final points:
• A frequent question I get is "Should I learn to improvise by thinking of chord tones or by thinking of scales?" Well, ultimately, you need to know both! The chord-on-chord approach calls on knowledge of scales as well as chords, since you need to know which scales a chord is related to in order to pick other chords from a related scale to play over the chord. The goal is to use your material creatively. It's okay to think about scales as long as you do something with them besides run them up and down! After all, arpeggios can be just as dull as scales.
• Another question that crops up is "Do I really need to know all this theory?" My answer: No, if you're the kind of person who can just instinctively hear and play everything you'll ever want to play! To my mind, there are three main reasons for learning about music theory: first, so that you can better understand what you're hearing; second, because it can help you come up with ideas for new things to play; and third, so that you can communicate with other musicians more effectively. Music theory is a tool; like any other tool in life, whether it makes things better or worse depends entirely on how wisely and skillfully you use it.
I hope you'll have fun with this. As always, thanks for stopping by!