The purpose of this article is to make you aware of what notes to omit from a chord if needed and how to tell what chord/scale is best suited over what harmony.
Whilst not 'advanced', this topic is not entirely well documented and you would do well to absorb the information here and make note of the 'correct' way to do things. Remember these are just guidelines and if it sounds right to you, then do it.
let's consider a guitarist. A typical guitarist has 4 fingers on his fretting hand at his disposal and has 6 strings.
Suppose he wishes to accompany the lead player by playing a 13 chord, this chord has 7 notes in it (1-3-5-7-9-11-13). Since the 13 chord has 7 notes and the guitar only has 6 strings, it is vital that a note is omitted in order to accomodate the rest of the chord. So, how do we know which notes to omit?
There are a few simple rules to determine which notes should stay and which should go. Take a look below:
- The fifth is usually the first to go, it has no crucial function in most chords and usually just serves to add an extra voice to the chord.
- In the case of the 13 chord, the 9 can go. Whilst it does add a nice extra texture to the 13 chord, it is not necessary to define the sound of the 13.
- The 11 can go. The 11 (unless sharpened) follows the same function as the fifth and just serves to add more weight behind the chord
The remaining notes are your most crucial, you are now left with 1 3 7 13
Why are these the most important? Well...
- The 1st degree is the root of the chord and so in the majority of settings, is vital.
- The 3rd degree defines the chord, the 3rd will state to the composer/performer whether the chord is major or minor and so is extremely important to the harmony.
- The 7th states whether the chord is dominant or not and so in most cases is not omitted.
- The 13th is the whole reason of the chord. Without the 13th, the chord would not be a 13th and instead just a 7th.
These rules apply to all chords, if it was a ninth chord, the only note you would definitely get rid of would be the 5th (Leaving you with 1-3-7-9).
There are a few special cases however, remember when I said that the 1st degree is vital? Well it is, but who says you have to be playing it...
If you are in a band and are 100% certain that your bass player is going to be playing the root of all the chords throughout the song, then you will not need to have the 1st degree in your chord voicings since the bassist is already defining it for you.
The 7 note 13th chord (1-3-5-7-9-11-13) can be played as so: (3-7-13).
By applying basic logic to the fretboard, we have gotten rid of more than half of the notes in that chord. Not only that but now we are now much more forgiving on our hands and are not taking up the entire frequency spectrum!
Suitable scales and chords
Now that we've dealt with what notes to omit. It's time to analyze what those intervals are good for and how to tell what scale we can play over what chord and vice versa.
If we have the chord Am7, we have this:
A C E G
1 b3 5 b7
We should already be able to tell this won't work in a major scale. The most obvious hint is the b3rd which basically says "I am a minor chord", the less obvious one is the b7. The b7 is not present in the major scale, only in dominant scales and minor scales (including Locrian). So we can deduce that because the Am7 has both a b3 and a b7 it belongs to a minor scale.
There are many minor scales, so which one?
Well, we know that the formula for the Locrian mode is:
1 b2 b3 4 b5 b6 b7
And since there is a b5 in that mode, it will clash with the perfect fifth in the Am7 so A locrian is a definite no go. This has narrowed the choice of suitable scales down and the one to choose is up to the listener.
A few suitable scales would be
1 b2 b3 4 5 b6 b7
Natural Minor (Aeolian)
1 2 b3 4 5 b6 b7
1 2 b3 4 5 6 b7
The reason all three of these choices work with the Am7 chord is because they all contain the same intervals (1-b3-5-b7). At no point will there be any clashes and so you can be happy in knowing it's a safe bet.
Let's do a few more examples to hammer that point in.
Suppose we have a stripped down chord with the intervals (3-b7).
Immediately we should notice that this is ONLY suitable for dominant tonalities. The major third, mixed with the flat seven immediately means dominant.
Therefore the best choice for this small voicing is:
1 2 3 4 5 6 b7
because it contains both the major third and the flattened seventh.
And lastly, an odd example:
Suppose we have the intervals (b2-5).
It may not be obvious, but there is only one possibility. In a traditional major scale, the only presence of a b2 is in the phrygian and locrian modes.
And since we know that the locrian mode consists of a b5, we can be sure in knowing that the intervals (b2-5) will not work over the locrian mode and that leaves us with the phrygian mode.
1 b2 b3 4 5 b6 b7
Working the opposite way
Things get slightly more complicated when we work the oppoiste way, that is, trying to figure out what scale can work with what chord. The reason it is more difficult is because of the amount of possibilities that the scale can give and choosing the most suitable one at the time.
One of the best examples I can give for this is one of my own and is very rarely used for what I consider it to be used for.
Let us take the half-whole scale. The formula for the half-whole scale is as follows;
The sheer amount of tones lends itself to major ambiguity. Just from looking at it, this scale could work over-
- A minor chord - because of the 1-b3-5
- A major chord - because of the 1-3-5
- A diminished chord because of the 1-b3-b5
That's an awful lot of possibilities given the fact that most scales can only deal with one tonality whereas this scale can work with three!
This is where ambiguity comes into play. The reason the half-whole scale is mostly played over diminished chords is because with the other two (major and minor) possibilities, it will sound outside. How many major scales do you know that have a b3,b5 and b7 ? Now you know one.
Considering all of the possibilities of scales-to-chords and chords-to-scales you should now be able to find something to suit your needs.
Hopefully this article has shed some light on systematically eliminating unsuitable chords and scales from your progressions.
Now, go forth and improvise!