Steve GypsyJazz

B half diminished 7 = Bm7b5 = Bm7-5. With Bm7b5 being the most common.

A 'diminished' chord is made up of these notes:

1st, min 3rd, flat 5th, double flat 7th

(double flat 7th is the same note as the major 6th, but it's usually written as double flat 7th)

So A diminished would be : A, C, Eb, Gb

As a point of interest, the intervals between successive notes in a diminished chord are ALL minor thirds.

This means if you start to build a dim chord on a C, you end up with the same notes as for the A dim.

In other words Adim = Cdim = Ebdim = Gbdim = A+C+Eb+Gb So when you play a diminished chord, if you move it up the neck by 3 frets you will still have the same chord!

To answer your question Steve, there is also a chord called the half-diminished, or diminished 7th. I usually write this one as something like Em7b-5 - just another name for the same chord. (It's best if you're aware of the different names used for the same chord). It is also sometimes written with a small circle with a line through it.

The difference between this one and a 'normal' diminished is that the 7th of the chord is a flat 7th not a double flat 7th (hence half-diminished).

So the spelling is 1st, min 3rd, flat 5th, flat 7th

So B half diminished (or Bm7b-5) = B D F A. I'll leave it up to you to sort out the fingering!