The fun doesn't stop with the m7b5 chord! We can also create what is known as a 'whole diminished' chord using the 7th. This chord retains more of the intensity of the original diminished chord and has a different usage to the m7b5. We discover all in this lesson!
Our second diminished chord is known as both "diminished 7th" and "whole diminished". The difference between this diminished chord ad the previous is that you have got a flat, flat seventh! Yes you read it correctly, you flatten the 7th note twice. When you do this you get the same b3rd interval (3 frets) between each note in the chord, which explains this concept of 'whole' diminished versus 'half'. The formula altogether is therefore 1st, b3rd, b5th & bb7th, as shown here:
To help you put this into practice, here is a common shape for the diminished 7th in the key of E (as per the example above). Notice the notes on the neck as you go through it, trying to say the degrees of the scale (i.e. 1st, b3rd, b5th etc...).