Watch the Dominant Soloing 2: 12 online guitar lesson by Brad Carlton from Bluesology 1
We'll open this lesson with a demo of the minor 7th flat5 chord, also known as a half-diminished chord, played over a dominant 7th chord. For C7 we will use the half-dim chord a major third above the root, i.e. E half- dim. If you spell out the chord, E-G-B flat-D, you will see, if analyzed as a C9th chord, you have the 3-5-flat7-9.
Check out the sound of the IV9 played over the I chord in the second part of this lesson. Lots of possibilities here!