Greetings and welcome to todays episode of my guitar blog.
Let´s talk about the half diminished chord:
The half dminished chord or minor 7 flat 5 chord (m7b5) is based on a diminished triad with a flat 7. A diminished triad is symmetrical in the formula root – b3 – b3 so the interval from root to the last note is no perfect fifth. It´s a flatted fifth (b5). The half diminished chord has the chord formula root – b3 – b5 – b7
In a major scale, this chord is harmonized on the 7th degree of the major scale and is related to the locrian mode. You can find it also in other scales like harmonic or melodic minor.
If you compare the half diminished chord with a diminished 7 chord you will see that the triad is the same, but the b7 seven now is a bb7.