Simpedia

Ian B., California

Good question. The accompaniment program chord diagrams are intended to teach “inheriting” of various chord types based on the original root position “triad” voicing. Whereas, the Dim7 is not based on a triad, I would not recommend using this method.

I recently made the mistake of trying to teach this to a student by starting with the diminished chord diagram. But explaining the actual -7 note brought a lot of confusion. Now I believe that is easier to explain AFTER students reach the level of playing 7th chords in the blues and Improv program, with the 7th voiced on top of the triad (root position). Once that version of a 7th chord had been established, it’s much easier to inherit the diminished version of 7th chords.

Anna J., Canada

I was actually just reviewing the Moonlight Sonata materials from level 14 yesterday which gets into this a little…it is a 4-note chord. I think of it as taking a 7th chord and bringing the top 3 notes down a half step. So C7 would become C-Eb-Gb-A

In a C7 chord the top note would be Bb (though in Accomp 1, we play it on the bottom)…bring that down a half step gets you to A.

To confirm you have the right notes, you can check that they are each 3 half steps apart.

Gordon Harvey, Australia

To make a dim7 chord in the accompaniment context, you would just do the same thing as the diminished triad (middle and top notes down a half step) plus bring the bottom note down a step and a half. If that’s too much for the student to wrap their head around, they can just play the triad and it will sound fine. In my experience dim7 chords are pretty rare in the accompaniment arena.

In jazz, you could initially tackle the dim7 using the Jazz Clues – they will just have a small new instruction. For Jazz Clue 1, you will move the top note down a half step from the usual placement, in other words flat the 5. For Jazz Clue 2, you’ll move the octave down by 1 1/2 steps instead of one or two half steps, so that Cdim7 would be C and A.

To figure out all four notes, I think the easiest way is to apply the accompaniment rule for making the diminished triad then add the rule for Jazz Clue 2.

All the above is simpler in practice than I make it sound! I’d just spend enough time doing it for myself so you can show it to the students with ease. That said, other approaches discussed here can be valid too, again so long as you are confident with them.

Once you have a handle on working them out, there are some very cool visual and structural features to the dim7 chord that make it uniquely easy to process. That would take a little more time to explain here. One of them has already been mentioned by Anna J – the fact that all the notes are three half steps apart.

Mark M., New York

In addition to Gordon’s advice, another simple playing-based way of doing a dim7 chord is to make a split chord by keeping the LH as is but moving the RH to play a simple dim chord based on the flatted-3, i.e., the note that would make a chord minor. E.g., C’s middle note is E. Cm moves that note down to Eb. So just move your RH finger 1 there and play a basic Ebdim in your RH while keeping C in the bass.

Maureen K., California

The extra cool thing to teach about dim 7 chords are that there are only 3 of them. You find, as others have said above, that Cdim7 has the notes C Eb Gb A. Find your Eb dim7, your Gb dim 7, and your Adim7 and you’ll find they all have those same notes… you just change the root note.

Robin T., Australia

Maureen K From a mathematical point of view which I always like to explore in music
As there only 12 different notes available in an octave, if the distance between the notes is the same (ie a minor 3rd or 3 semitones apart so 12/3 = 4) then the chords all have to be the same.

Maureen K., California

Robin T Huh. I guess another chord that does that is the augmented. (3-note chord.) 4 semitones apart. There are 4 of them. Cool.

Mark M., New York

Normally I like avoiding technicalities in discussion here, but the following technicality can make it easier to properly identify the names of the notes of a dim7 chord: a dim7 chord is made of the 1, the flatted-3, the flatted-5, and the *double-flatted-7. In a dim7 chord, the name of the interval for the 7 note is the diminished 7 — a double-flatted 7 — as opposed to the single-flatted 7 used in regular 7 and m7 chords, which is an interval called a minor 7.

So Bb is the correct name for the “7” note in a C#dim7 chord. Why? Because the regular “7” that’s part of the C# major scale is B#. Flat it once, it’s B natural. Flat it twice, it’s Bb. Very convenient that double-flatting a note with a sharp name gives us a name that’s familiar.

Not so in other cases. A Cdim7’s notes are C, Eb, Gb and, believe it or not, the proper name for the final note is B-double-flat. Yes, it’s physically the same as A natural on the piano keyboard. And so it’s totally common / normal / helpful / efficient to think of it as simply A natural. That can make it easier to find and play. But the proper name is B-double-flat in this case. Because in the C scale, “A” is 6 and “B” is 7. So any type of 6 needs to be based on the letter A, and any type of 7 needs to be based on the B. So A would not be the proper letter name to identify the “7” that’s part of a Cdim7 chord. B-double-flat is. (And A# would, similarly, not be the proper name for the top note of a C#dim7.)

But again, this is all only important if you want to properly *name* the notes of the dim7 chord. If you’re just out to play them, it’s just as well not to worry about this.