Guitar chords in the key of C# or Db:
Chord Db7-5 (9th fret) notes: Db, Abb, Cb and F. (Abb is A double sharp or G and Cb=B).
You must leave out the 2nd and 1st strings.
Db(C#) dominant 7th flat 5th guitar chord's alternative names: Db7b5, Dbdom7b5.
1(C#/Db), 3(F), b5(G/Abb), b7(B/Cb).