Core tones in chords

Question

Hi hopefully someone can clarify this concept for me.

When studying music I was introduced to the concept of 'core tones' within chords. These being the 3rd and 7th as they separately define the quality of the chord.

The third defines major or minor while the seventh defines major or dominant. As far as I remember they defined the flat seventh in a minor chord as a dominant seventh...

The idea being that if I need to I can omit the non-core tones (the 1st and 5th) and build the harmony around just the defining third and seventh, adding extensions to the 3rd and 7th to achieve the same overall effect.

After a relatively exhaustive internet search i have come across NO references to this anywhere else.

Is this accepted musical theory?

Answer 1

Omitting the 5th of a chord is very common and standard practice in classical harmony theory.

I would cite one reference as "Basic Theory-Harmony A Text and Work Book for the School Musician" By Joseph Paulson, Irving Cheyette, 1951.

I have never heard of omitting the 1 from a chord in classical music theory but learned "on the street", so to speak, that this was okay to do. The rational for NOT omitting it is that the 1 simply IS the identity of the chord and A7 = (A, C#, E, G) without the A is NOT an A7 in any way, it is a C# diminished triad. However, the rational for relaxing this is that the movement from C#dim --> D has the 7-->8 and 4-->3 that we want to hear in a cadence so the movement viio --> I is a good replacement for V7 --> I. In classical music theory viio --> I is called a Leading Tone Cadence and is considered separate from the "Authentic Cadence" V7 --> I. In a branch of music theory called Functional Harmony these might be considered the same thing, i.e. the serve the same purpose or perform the same function. Since the vii is a 3rd away from the 1 of that chord it also fits in nicely with the concept of chord substitution. In most cases a chord can be replaced by one that starts on the 3rd degree and will serve the same purpose. This does not explain the concept of "core" tones but does explain to some extent why it is acceptable to remove the 1 of a chord. The other rational for a guitarist might be to make the chord easier to play. We do this a lot, and it can drive other musicians nuts.

I too have NEVER heard the term core tones. It could be someone's own jargon for describing the tones that are considered most important.

I will say this w/r to "important". It's not the note that is important but the interval it creates when heard against the other notes in a chord. The 3rd and 7th form an interval of a 5th (or dim 5th). If you throw away the 1 you will never hear the quality of the chord that tells you if it's major or minor. In fact if you take the 1 away from a Maj 7th chord you are left with a minor triad on the 3rd degree. You have completely thrown the definition of what the 3rd is in the garbage. So, it's not the presence of the 3rd that tells you if a chord is Maj or min but the presence of the 1 and 3 together. To the extent that omitting the 1 sometimes works, that has to do with the chord's "function" and where it's going (not so much what it is). Applying chord subs without the context of movement within a progression can lead to interesting sounds but mostly this is meaningless relative to the original intent.

Answer 2

The term 'guide tones' is how I've heard this concept described. For example,

Guide Tones
The Guide Tones are the 3rd and 7th of a chord. They are the most harmonically important notes of the chord. This is because they determine the quality of the chord – whether it’s Major, minor, minor-Major or Dominant.
(thejazzpianosite.com)

This idea comes up frequently in jazz. In voicing chords, pianists often will just play "thirds and sevenths", because they provide sufficient harmonic context while allowing melodic and harmonic freedom around them. Playing complete chords on the piano, for example, is likely to interfere with the bass player, or a soloist who is looking to play "outside" the principle chord.

There are also technical advantages in that by leaving out the root and fifth, it opens up voicings that would be otherwise difficult to span. C9 played without the root is easy to play with one hand, requiring a span of a seventh (from E to D); whereas, including the root requires a ninth (C to D).

In the particular case of dominant seventh chords, the "thirds and sevenths" approach makes tritone substitution trivial. For example, the third and seventh of G7 are B and F, respectively, which are in turn the seventh and third of Db7.

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EDIT

See also In jazz, what is a guide tone?

Answer 3

Some tones of a chord can be omitted while other tones are essential for defining the chord.

In jazz there is a rootless chord voicing, but don't confuse that with a true root omission. It's typical that a bass part will play the root while some other instrument play rootless chord voicings for part of the accompaniment. Also, shells are another kind of jazz accompaniment chord that are incomplete, but the other musical parts often supply additional tones which fill in the harmony.

Have said that about root omission, there is one common chord that is sometimes described theoretically as a root-omitted chord: the diminished seventh chord. If you take a dominant ninth chord in the minor mode and then omit it's root, the remaining chord is a diminished seventh chord built on the leading tone. As the chord is theoretically derived from a dominant chord, the diminished seventh leading tone chord is then considered a type of dominant chord.

Otherwise it's not normal to omit the root from a chord.

The third of chord is more or less required. It give the basic chord quality of major or minor.

The fifth of most chords will be a perfect fifth. Diminished fifths would typically indicate a chord built on a leading tone or a subdominant iio chord in minor. In jazz diminished or augmented fifths are typical of altered dominant chords. The fifth is often omitted unless a diminished or augmented fifth is needed to make clear diminished or altered chords.

The seventh is required for seventh chords.

Extensions beyond the seventh - ninth, eleventh, and thirteen - usually need the seventh to be present along with the extensions.

So, omission of chord tones depends greatly on the type of chord that will be implied. A reasonable list of essential tones is:

• triads need the root and third
• seventh chords need the root, third and seventh
• extended chords need the root, third, seventh and extensions

...The idea being that if I need to I can omit the non-core tones (the 1st and 5th) and build the harmony around just the defining third and seventh, adding extensions to the 3rd and 7th to achieve the same overall effect...

With dominant chord, yes. This is sort of like the omitting the root on a dominant ninth to make a leading tone diminished seventh chord. When a dominant's third and seventh (solfege TI and FA) resolve to the next chord's root and third (analogous to DO and MI) it's clearly understood as dominant harmony. This works because of the characteristic half-step motions of the leading tone and the subdominant degrees, and because the progression is ubiquitous in tonal music.

You might be more careful with other chords. If you omit the root from a vi7 chord (Am7 in the key of C major) you risk have the remaining tones (C E G) sounding like the plain tonic triad. That doesn't necessarily mean the harmony will be bad. Decide on what is important. If you really want the sound of the minor seventh chord, include the root and seventh. Generally speaking, don't omit essential chord tones.

Answer 4

As others have alluded to this is a very common way to play jazz and is particularly useful when playing in a band set-up where a bass player is playing the root (or at least implying the root) and there’s a requirement to carry the melody or improvise over the chords of the piece.