Same suggestion as with Trebor's latest song:
http://www.maximummusician.com/articlechordprimer.htmIn short:
Your song is in D major
D, G and A are I, IV and V
Em, F#m and Bm are ii, iii and vi
(D Em F#m G A Bm (jamstudio doesnt have VII chords unfortunately)
Any I chord can be replaced by a iii or vi chord
Any ii chord can be replaced by a IV
Etc
So D G A D (1st page of your song) could also be F#m G A D or Bm G A D.
Adds a whole lot more variety to your songs
