Originally Posted by bassybill  Just to clarify a little, using a root note of C...
Most chords containing a seventh usually contain the root note, the third note of the scale, the fifth note of the scale and the seventh note of the scale.
In the C major scale, these notes are C, E, G, B.
In the C natural minor scale, they are C, Eb, G and Bb.
Notice that it's the third and seventh notes that differ between the two.
Now, the rules you use when working out what notes are in a chord say that third notes are major by default. In other words, they're assumed to be major unless minor is specified. For sevenths, it's the other way around - they're minor by default.
So, look at this chord symbol: C7. We know it contains the root, third, fifth and seventh. We know that the root is C and the fifth is G (see above). We also know the third is major as this is the default, so the note is E. The seventh is minor by default, so the note is Bb. Cross-check this with the info above about the notes in major and natural minor scales and you'll get it.
Now, look at this chord symbol: Cmin7 (often written Cm7 - lower case "m"). We know the "min" bit must refer to the third, as the seventh is minor by default and so doesn't need stating as such. Our notes are therefore the root C, MINOR 3rd Eb, fifth G and minor seventh Bb. Cross-check with the above info again!
For Cmaj7 (or CM7 - note the capital "M"), the major must indicate a major 7th as the third is major by default. So, our root, major third, fifth and MAJOR seventh are C, E, G, B. Cross-check again!
To summarise for the key of C:
C7 = root, major 3rd, fifth, minor 7th = C, E, G, Bb
Cm7 = root, minor 3rd, fifth, minor 7th = C, Eb, G, Bb
CM7 = root, major 3rd, fifth, major 7th = C, E, G, B
(There's also the possibility of combining a minor 3rd with a major 7th, but such chords are pretty rare and you can forget about them for now.)
For other keys, you need to know the major and natural minor scales to work out the notes in these chords. For example, with D as the root:
Major scale - D, E, F#, G, A, B, C#, D
Natural minor scale - D, E, F, G, A, Bb, C, D
I've put the root, third, fifth and seventh in bold for each scale. Notice again that the root and the fifth are the same in both scales, but the thirds and the sevenths differ.
Chords would be "spelled" as follows (check these notes in the above scales):
D7 = root, major 3rd, fifth, minor 7th = D, F#, A, C
Dm7 = root, minor 3rd, fifth, minor 7th = D, F, A, C
DM7 = root, major 3rd, fifth, major 7th = D, F#, A, C#
All this may seem complicated, but after working with chords for a while it just becomes second nature. Try working out the notes in X7, Xm7 and XM7 chords. when X is any note picked at random, other than C or D that are done here for you!
I hope that helps. |
