#1
I am learning the chords for a song, and one of the chords is a D2. I have tried to work out how to play it, although I am not sure if its right. Is a D2 chord a D major chord with a second interval added? The way I was thinking of playing it was. Is that a D2 chord? or is it wrong?

E--0--
B--3--
G--2--
D--0--
A------
E------

Also in the chords I have for the song there is a chord written as "GM7". Is that a G minor 7? Because usually the "m" is lower case, and in other places on the music the "m" for minor is written in lower case.
#2
thats a Dsus2. wich is notated as D2, i guess. meaning the 2nd (E) is held over, so youre right. yeah its gminor otherwise it would be a major 7th Gmj7.
#3
If it's a capital "M," then it's a major seventh.
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