I have come across another theory question with these singer/guitarists I've been playing with. One of them brought a song with an "A/D" chord. The other guitarist thought that I should play an "A' as the root for that chord. I explained that that notation means that I should be playing "D". I have no question about this. What I want to clarify is if my playing my D with their A chord (A - C# - E) makes the A chord a Dmaj7. Thank you in advance for your replies.