When I played a music meet a D+9 and a A7/5+. I have tried search in google, but didn't find it. Does anybody know that?
It has two different meanings in the context of chords . Traditionally, the '+' symbol is used to denote an augmented triad, however it is also used to represent a raised interval which is typically represented by a sharp (#).
The first one is most likely an augmented triad with a 9th. The second one just treat the '+' as a sharp where you would play an A7 with a #5.
+= sharpened. Sharpened whatever. The number that has + in front of it(or by it) is raised by one semitone so +5 is a sharpened 5th and +9 is a sharpened 9th. The sign means augmented,when used in chord names, and the usual note that's augmented (taken up by a semitone) is the 5th. Thus A = A,C#,E, whereas A+ = A,C#,E#(F). It's common in jazz to alter 5ths and 9ths, so there is also an augmented 9th. Sometimes labelled +9, or aug9.
Note that '+' is different from 'add', even if it has the same connotation in maths.
I think the answer is much simpler than all the things everyone is saying as far as popular music charts. What I have seen is that a D+9 chord is a D F# A and an E on top differing from a D9 chord which is a7th chord which is D F# A C E. An A7/5+ is something I have not seen. If they are saying play a 5th in the bass then they are saying add the E in the bass which is the fifth of an A chord. The+ plus may be simply to add the fifth. A + sign to me is just saying add one more note not add all the thirds up to that note.