Guitar chords in the key of A:
Chord A7-5 (4th fret) notes: A, G, C#, Eb and A. You should not play the 6th string.
The string 5 (A) is left open.
A dominant 7th flat 5th guitar chord's alternative names: A7b5, Adom7b5.
1(A), 3(C#/Db), b5(D#/Eb), b7(G).