Adventures in Side-Slipping, Part 1
I first heard about a technique called "side-slipping" in David Liebman's inspirational book A Chromatic Approach to Jazz Harmony and Melody. My recent interest in the coscale relationship led me back to it, since both involve, at least initially, working with "scales" that have no root notes.
The basic idea of side-slipping is extremely simple. Imagine you're playing over an Am chord using the A Natural Minor scale. Now "slip" the whole fingering up or down a semitone; you'll find you're playing the Ab or Bb Natural Minor scale over the same underlying Am harmony. Conceptually, that's all side-slipping is.
In either of these cases, however, we have a problem of analysis because the pattern you're playing doesn't contain a root note. As a result we can't talk about it using the language of modes, the most natural way to do that kind of thing. After all, if you slipped your fingers down two frets instead of one you'd simply be playing A Locrian, and we all know (I hope) how to make sense of what's going on what we play A Locrian over an Am harmony. This is the kind of thing the Encyclopoedia does very thoroughly.
Let's look at what happens when we move the A Natural Minor fingering up the fretboard, one fret at a time, without changing the underlying Am harmony:
| Original fret | A Natural Minor | 1, 2, b3, 4, 5, b6, b7 |
| Up 1 fret | Semitone Side-Slip | #1 #2 3 #4 #5 6 7 |
| Up 2 frets | A Mixolydian | 1, 2, 3, 4, 5, 6, b7 |
| Up 3 frets | Minor Third Side-Slip | #1, #2, #3, #4, #5, #6, 7 |
| Up 4 frets | A Lydian | 1, 2, 3, #4, 5, 6, 7 |
| Up 5 frets | A Phrygian | 1, b2, b3, 4, 5, b6, b7 |
| Up 6 frets | Tritone Side-Slip | #1, 2, 3, #4, #5, 6, 7 |
| Up 7 frets | A Dorian | 1, 2, b3, 4, 5, 6, b7 |
| Up 8 frets | Augmented Side-Slip | #1, #2, 3, #4, #5, #6, 7 |
| Up 9 frets | A Major (Ionian) | 1, 2, 3, 4, 5, 6, 7 |
| Up 10 frets | A Locrian | 1, b2, b3, 4, b5, b6, b7 |
| Up 11 frets | Major Seventh Side-Slip | #1, 2, 3, #4, 5, 6, 7 |
| Up 12 frets | A Natural Minor | 1, 2, b3, 4, 5, b6, b7 |
This isn't surprising to most of you, I'm sure; any non-symmetrical n-note scale will contain n modes and 12-n of these things that have no root note, which most people ignore. Let's do the opposite and remove the modes from the list, since we already know how to deal with them. What's left are what I'll call the side-slips:
| Up 1 fret | Semitone Side-Slip | #1 #2 3 #4 #5 6 7 |
| Up 3 frets | Minor Third Side-Slip | #1, #2, #3, #4, #5, #6, 7 |
| Up 6 frets | Tritone Side-Slip | #1, 2, 3, #4, #5, 6, 7 |
| Up 8 frets | Augmented Side-Slip | #1, #2, 3, #4, #5, #6, 7 |
| Up 11 frets | Major Seventh Side-Slip | #1, 2, 3, #4, 5, 6, 7 |
These resources are worth exploring in a number of ways. One is simply to examine their tensions against the underlying chord and treat them as "extra modes"; I think this can work well with scales with fewer notes, as I suggest in the Encyclopoedia when I treat all twelve "modes" of the 3- and 4-note arpeggios. I'm a bit more sceptical about this way of approaching scales with seven or more notes, since the level of dissonance is quite a challenge to work with, but it may very well be worth further investigation.
I mentioned that I got into this by way of coscales, since I'm currently interested in ways to use all twelve tones of the chromatic scale in a structured way by "sharing" them between one or more scales. Let's imagine we're going to play the Natural Minor and one of these side-slips, in fairly quick alternation. What notes would be be playing?
| Natural Minor + Semitone Side-Slip | Total chromatic |
| Natural Minor + Minor Third Side-Slip | 1, #1, 2, #2, #3, #4, 5, #5, #6, 7 |
| Natural Minor + Tritone Side-Slip | Total chromatic |
| Natural Minor + Augmented Side-Slip | 1, #1, 2, #2, 3, 4, #4, 5, #5, #6, b7, 7 |
| Natural Minor + Major Seventh Side-Slip | Total Chromatic |
So, we have three side-slips that give the total chromatic when combined with the original scale. The other two side-slips create very nearly chromatic scales of ten and eleven notes. Remember that all this is specific to the scale in question -- the Natural Minor or Aeolian scale -- and other scales will behave differently.
The approach I'm taking with these right now is the same one I take with coscale relationships (note that these are not coscales, since there is some overlap in the two scales!). I'm constructing lines that alternate quickly and freely between the two scales, playing a few notes from one and then a few from the other, and so on. This has a tendency to cover all twelve notes in a short time, giving a fair approximation of a serial texture. Of course, many things that make serial music work are missing from this approach, but what you get in return is a fairly flexible framework for improvisation. Into this framework it may be possible to reintroduce Schoenbergian ideas as a way to further structure the music without giving up on our ability to improvise with it: such is the hope, anyway.
Here's a recording of me jamming with the Major Seventh Side-Slip of the A Natural Minor Scale. It's a bit sloppy -- you have to think fast when doing this, and my fingers aren't quite keeping up yet! -- but I hope it helps you hear some of the sounds that are possible and decide whether this is worth your investigation:
