This is from something I was doing a few months ago. Just a reference page, not in order. Possibly mistakes. Let me know. But this is kind of the way I look at using triads melodically.
All of the "G" chords are simply G with whatever melody note on top. So, G chord with A in the melody, I'd be playing the Gadd9 shape.
Note: usually I wouldn't give this to someone all at once. Generally give them just specific voicings for playing a simple tune or whatever.
http://chordsologuitar.com/wp-conten...ith-Triads.pdf