Stim's last suggestion (To make things simpler....) is really a different thing: namely a b5 substitution. This is a common thing in jazz playing, replacing a (possibly altered) dominant seventh chord with a (possibly altered) dominant 7th chord on the note a b5th above the original dominant chord's root (if you see what I mean!). You can replace, for example, a G7 chord with a Db7 chord, Db being the b5 above G.

This relies on the fact that the characteristic sound of a dominant seventh chord is primarily from the tritone between the 3rd and the b7 of the chord: in G7 [G B D F] this is the interval B-F. If we now look at the dominant 7th chord a b5 above G ie Db7, we have the notes Db F Ab Cb=B and in this chord the interval from the 3rd to the b7 is the tritone F-B. And since the inversion (changing the order of the two notes) of a tritone is a tritone, this has the same characteristic sound as in the G7 chord with the notes reversed.

Playing Eb7 is not the same as playing A7b5, ie the notes of the two chords are not the same. It is a substitute chord that may (in the right circumstances) be used to replace the A7b5 chord. As I said at the start of the post this is a very common thing to do in jazz playing.


Mick