Diminished, Diminshed 7th and half-diminished or m7b5 chords

It's been a very long time since my last post, but I said I'd be looking at diminished chords. 

Diminished Chords
A bog standard plain diminished chord, is in reality nothing more than a standard minor chord triad (which as I've stated before has a scale spelling of 1, b3, 5) and flattening the 5th note as well. So going back to C you'd get.

1 = C
b3 = Eb
b5 = Gb

So this would be called a C diminished chord.

Half-Diminished or m7b5 chords
So how do we make it a half-diminished chord. Well bizarrely a half-diminished chord is really a minor 7th chord (remember the scale spelling for that 1, b3, 5, b7) but with the 5th flattened also, so you get 1, b3, b5, b7. So again in  C.

1 = C
b3 = Eb
b5 = Gb
b7 = Bb

So if you think about this as it's a minor 7th chord with a flattened 5th, it's become more popularly known as a minor 7 flat 5 (m7b5) chord and certainly in popular music you'll find more people who know it by that name, rather than half-diminished.

Diminished 7th chords
So how do  you make a full diminished 7th chord.

Pretty easily actually. All you need to do is take a half-diminished (m7b5) chord and flatten the 7th note AGAIN. Yes that's right again. So the scale spelling of a diminished 7th chord is 1, b3, b5, bb7. 

So again in C you get these notes.

1 = C
b3 = Eb
b5 = Gb
b7 = Bbb (yes music theory caters for double flats so whilst it's actually the same note that we'd generally call A it's called Bbb).