If I play the chord: GBDA, then this is considered a Gadd9. But if I play the 3rd above the 5th (GDB), it is not called a 10th.
Why don't we refer to all notes by 1-7, and is there a system to picking higher numbers (11) vs lower ones (4)?
The distinction is between interval distances (2nd -> ∞) and chord tones (root, 3rd, 5th, 7th, 9th, 11th, 13th).
When you play Gadd9, you are adding the chord tone that is a 9th above the root. If we just played a G9 chord, the dominant 7th would actually be implied (G-B-D-F-A).
Playing the interval of a 10th above the root (like G-D-B) doesn't change the chord. All that does is displace the chord tone (in this case, the 3rd) up one octave, so it's still called a G major triad.
So, a note would be described as a fourth if we were talking about interval distances, and an 11th if it was a chord tone (typically preceded by the root, 3rd, 5th, 7th, and 9th).
The exceptions are sus chords and 6 chords. A sus chord would typically have a 2nd or 4th above the root suspended in the middle of a triad voicing, often substituting for the third (like C-D-G or C-F-G). A 6 chord substitutes the 5th of the chord with a 6th, but maintains the same function of the original chord.
THE difference between 2nd and 9th or add ninth is not really the octave you play the extended notes in; the same with 4th and 11th. It is simply whether you include the dominant seventh or not. Generally speaking it makes sense to stack extended chords in their original positions but take the c9 chord-c e g bflat d. NOW try this inversion which is kinda a g minor 6th with c bass
bass c g bflat d e. THE same notes are played but just have a different texture.
JUST with reference to Steve's post which is highly informative. A g2 chord would not contain the major third hence it would like G,A,D. THE G A B D CHORD is G add second or G add ninth, YOU don't need to worry about the octave the A is in; what determines its character as an add ninth is the fact that the dominant seventh has not been included. THE same is true of whether a chord is a sixth or thirteenth. TAKE G sixth G B D E IN ROOT POSITION; now consider this chord Bass G F A B D E.THE sixth is now a thirteenth because the dominant seven-f-regardless of its position- has been placed in the mix. THE A is the ninth and I have omitted the eleventh to avoid too cluttered a harmonic feel. GUITARISTS have to be sparse in their interpretations of extended chords due to the limitations of guitar as opposed to a keyboard. BUT the dominant seventh is the pathway to extended chords, OFTEN on guitar the fifth will be sacrificed among others. Sparse interpretation of D13 would be D F SHARPE C B
These numbers come from the figured bass system of composition and performance, wherein roman numeral symbols (
I-ii6-V7-I) are written under a bass line indicating to the performer what inversions to use in the chords. The roman numerals refer to the chords built on each of the diatonic scale degrees (in C major
When you see something that says
Gadd9 its asking you to play the 9th scale degree above the root of the chord. If G is the root, A would be the 9th diatonic note above it. This indicates that the A is supposed to be played above the 5th (D). If you played A in the lower octave the chord would be a G 2nd chord (G-A-B-D).
Essentially the number is there to let you know what octave to play the dissonant note (7th, 9th, 11th). In a G major chord, 4 would most likely be referring to playing a C above the B but below the D, while 11 would suggest playing C above the D.