This is how to play the D Major Triad on the bass. D Major Triad is made up of 3 notes that come from the D major Scale. The root D, the 3rd which is F Sharp and the 5th which is A. We can play 2 octaves of that Triad by playing our open D string and then playing our low F Sharp which is the 2nd fret on the E string. Now our open A, now back to the D. F sharp which is 4th fret on the D string, A 7th fret on the D string and then we can grab our high D, 7th fret on the G string. So this is the 2 octave D Major Triad...and that the D Major Triad on 2 octaves on the bass guitar.