Before indulging ourselves into the tasty world of seventh chords, let’s review how we got here:

  • The diatonic major scale is made up of a specific sequence of half-step and whole-step intervals.
  • Every diatonic major scale has the exact same sequence of half-steps and whole-steps.
  • The key of C is the only “natural” diatonic major scale – all other keys require either sharps (#) or flats (b) to obtain the diatonic major scale sequence or “structure”.
  • Other than C, all keys are either sharp or flat – never both.
  • Chords come from scales – by selecting every other note.
  • Every diatonic key has seven chords – each note in the scale is the root of a chord.
  • The “every-other-note” intervals in chords are called “Thirds”
  • There are two types of Third intervals:  major or minor.
  • Triads are made up of three-notes – or two third intervals joined together.
  • Major triads have a major third, joined with a minor third.
  • Minor triads have a minor third, joined with a major third.
  • There is a specific sequence of chords in every key – all keys have the same exact sequence.

If you are unfamiliar with any items outlined above, I strongly recommend reviewing the appropriate previous blogs.

Again, we learned that chords always follow a specific sequence in every key.  Before adding the 7th onto our chords, let’s take one last look at the key of C triads before bidding farewell:

I    IImi    IIImi    IV    V    VImi    VIImi-5
C    Dmi     Emi      F     G    Ami     Bmi-5



Now let's compare the same chords with the 7th added on:


I       IImi     IIImi     IV       V     VImi     VIImi-5
Cma7    Dmi7     Emi7      Fma7     G7    Ami7     Bmi7-5



So just what the heck is going on here? Well, we’re just doing the same thing we did with triads – selecting every-other-note; except now instead of just picking out the first three notes, we’re grabbing one more.  Here it is starting on C:


1                3          5              7


C       D        E  F       G       A      B  C



That’s it?  You mean to tell me this ain’t rocket science? Nope – hate to disappoint you.  Remember, C to E (root to 3rd) is a major 3rd – then E to G (3rd to 5th) is a minor 3rd.  In steps, the triad structure is 2 + 1.5.


Our new interval between the 5th and 7th (G to B in this case) is major 3rd.  So, the structure for our C major seventh chord is:  2 + 1.5 + 2:


1       3       5      7   =  Root, 3rd, 5th, 7th


C       E       G      B   =  C major seventh (Cma7)


    2       1½      2      =  Major seventh structure



So what happens if we start on D? Glad you asked.  Remember, D is our second note in the key of C, and resulted in a Dmi triad.  Adding the 7th, we get:


       1          3             5          7


C      D      E   F      G      A      B   C



Our new interval between the 5th and 7th (A to C in this case) is minor 3rd.  So, the structure for our D minor seventh chord is:  1.5 + 2 + 1.5:


1       3       5      7   =  Root, 3rd, 5th, 7th


D       F       A      C   =  D minor seventh (Dmi7)


     1½      2      1½     =  Minor seventh structure


Take a long close look!  Compare the major seventh structure with the minor seventh structure:


2       1½      2      =  Major seventh structure
1½      2      1½      =  Minor seventh structure



Notice the intervals for major seventh add up to 5½ – while the intervals for the minor seventh add up to just 5.  Just as there are two types of third intervals, minor 3rd and major 3rd, there are two types of seventh intervals – minor7 and major7.


Take a closer look at our 7th chords in the key of C, and notice the I and IV chords are major 7th:  Cmaj7 and Fmaj7.


Also, notice the II, III, and VI chords are all minor 7th:  Dmi7, Emi7, and Ami7.


So, what’s with the V chord being called just G7 and not Gma7? Well, let’s see what happens when we choose every other note starting from G, the 5th note in the key of C:


                 1         3      5      7


C    D    E F    G    A    B C    D    E F



Our new interval between the 5th and 7th (D to F in this case) is minor 3rd.  So, the structure for our G seventh chord is:  2 + 1.5 + 1.5:


1       3       5      7   =  Root, 3rd, 5th, 7th


G       B       D      F   =  G seventh (G7)


    2       1½      1½     =  Dominant seventh structure



Dominant seventh? Yes, this is a whole new animal – the likes of which happens to be a point of confusion with many people – but really should not be.  First, no worries on the fancy name – get over it – there is a logical explanation, but first let’s compare this “new animal” with our other two animals:


2       1½      2      =  Major seventh structure


1½      2      1½      =  Minor seventh structure


2       1½     1½      =  Dominant seventh structure



As you can see, the dominant 7th chord starts out like a major 7th chord, that is, it has a major triad in front.  Then, we tack on a minor 7th at the end – so we get this sort of hybrid chord.  A dominant 7th chord is in fact simply a major triad with a minor 7th interval.


If you add up all the intervals, the dominat 7th chord results in 5 steps, just like the minor 7th chord did – they are just arranged in a different order.  Similarly, the interval between the root and 7th is minor 7th in both cases.


Protocol dictates we indicate major 7th (Cmaj7) minor 7th (Dmi7) and in the case of dominant seventh we simply call it a 7th chord (G7).


The dominant 7th chord, or just 7th chord, are by far the most interesting and happen to be my favorite.  I could spend several blogs talking about just this one chord.  For now, remember it only occurs on the 5th degree of a major scale in every key – and there is only one!


Last but not least:  The seventh degree of the major scale produces our beloved mi-5 chord – which like the 7th chord, there is only one – and in fact, the mi7-5 and dominant 7th chords share a unique trait I will discuss later on.  For now, here is what happens when we add a 7th to our Bmi-5 chord:


                         1          3          5         7


C   D   E F   G   A      B   C      D      E   F    G    A



Our new interval between the 5th and 7th (F to A in this case) is major 3rd.  So, the structure for our B minor seventh flat 5  is:  1.5 + 1.5 + 2:


1       3       5      7   =  Root, 3rd, 5th, 7th


B       D       F      A   =  B minor seventh -5 (Bmi7-5)


     1½      1½     2      =  Minor seventh flat 5 structure



Adding up all the intervals, we get 5 steps – so the 7th interval is minor.  This chord is very much like a normal minor 7th chord, except it just has the flat fifth – which we will discuss much more later on.


Whew!  That was our longest post yet, and a lot of information to assimilate.  Take a deep breath, relax…and realize though it seems like a lot, there is a lot of redundancy here.  Try not to focus too much on the dominant 7th or the minor 7-5 chords right now – and just look at the overall concept of how chords are built from scales.  Simply every other note is all you should be focusing on for now.  Chords have structures just like scales have structures – and in fact, it is the structure of scales that determines the structures of chords.  Keep that your main focus, and until next time I remain,


Musically yours,


Al