Originally posted by river
if i was writin a song with a G D A Bm in it i'd
be thinkin key o D. cant be A cuz G aint in A and
cant be G cuz A is minor in G. triad is the 1,3,5
notes of any scale. ya play em together as a chord.
in C thats CEG to minor it ya flat the 3rd , C Eb G.
a ( very breakable but still usable) rule when lookin
is if ya see two major chords a step apart( thats
two frets difference) the higher one is the 5th to
the tonic. (if i see a D and a C the D is 5th to G so
its in the key o G. but there are no rules which
are not made to be broken so if ya can find a way to
make somethin sound good thats against the rules you will
be loved by some and hated by some. im a rulebreaker
myself :)

Note: useing G D A Bm the key could be Bminor.
The Bm has a D note in the chord.
Plus these chords can be used in the keys of A and G
as Accidentals chords.

Mark