Three practical dim7 drop 2 voicings for guitar. I'm using Gbdim7 and Bbdim7 to make the inversions fit nicely within the twelve first frets:
Gbdim7 and Bdim7, Gbdim7
Here's the four inversions of these voicings.
Gbdim7 » Gbdim7 » Gbdim7 » Gbdim7
Bdim7 » Bdim7 » Bdim7 » Bdim7
Gbdim7 » Gbdim7 » Gbdim7 » Gbdim7
Lowering a note in a dim7, yields a dominant 7th. Let's start with a voicing of Gb diminished seventh:
Gbdim7 «» lower Eb to D = D7
Gbdim7 «» lower Gb to F = F7
Gbdim7 «» lower A to Ab = Ab7
Gbdim7 «» lower C to B = B7
If you repeat the process for the inversions of dim7, you'll get the inversions of the dominant 7ths
Gbdim7 «» lower Gb to F = F7
Gbdim7 «» lower C to B = B7
Gbdim7 «» lower Eb to D = D7
Gbdim7 «» lower A to Ab = Ab7
Reapeating the same thing for the next inversion of Gbdim7
Gbdim7 «» lower A to Ab = Ab7
Gbdim7 «» lower Eb to D = D7
Gbdim7 «» lower Gb to F = F7
Gbdim7 «» lower C to B = B7
And again
Gbdim7 «» lower C to B = B7
Gbdim7 «» lower Gb to F = F7
Gbdim7 «» lower A to Ab = Ab7
Gbdim7 «» lower Eb to D = D7
The four inversions of the dominant 7ths. It's a good idea to practice playing these inversions in all keys
D7 » D7 » D7 » D7
F7 » F7 » F7 » F7
Ab7 » Ab7 » Ab7 » Ab7
B7 » B7 » B7 » B7
If you raise the C in your D7ths, you'll get Dmaj7ths. Here's the four inversions of Dmaj7:
D7 «» Dmaj7
D7 «» Dmaj7
D7 «» Dmaj7
D7 «» Dmaj7
If you lower the F# (3) of the D7ths to F (b3), you'll get D minor 7th.
D7 «» Dm7
D7 «» Dm7
D7 «» Dm7
D7 «» Dm7
Dm7b5 from Dm7: Lowering the A's (5) of the Dm7s to Ab (b5).
Dm7 «» Dm7b5
Dm7 «» Dm7b5
Dm7 «» Dm7b5
Dm7 «» Dm7b5
Summary
Gbdim7 » D7 » Dm7 » D7 » Dmaj7 » Dm7b5
Gbdim7 » D7 » Dm7 » D7 » Dmaj7 » Dm7b5
Gbdim7 » D7 » Dm7 » D7 » Dmaj7 » Dm7b5
Gbdim7 » D7 » Dm7 » D7 » Dmaj7 » Dm7b5
Practice playing the octaves of the notes in Gbdim7:
1 (root): Gb
b3: A
b5: C
bb7: Eb