Watch the Slip Sliding online guitar lesson by Matthieu Brandt from Guitar Lab: Triads and Hendrixian Double Stops
It's gonna help you seeing where the scale is in relationship to the different triad shapes and possible doublestops that fit on top of the chord that's being played. At this point we're sticking quite close to triads from one key.
Although the notes you can use in your backing all stem from the same scale, on each separate triad, different notes will sound strong and others will sound weak. Obviously chord tones will sound the strongest when you target them in your backing arrangement.
In this lesson we'll research the underlying scales and learn to look upon each chord (triad) as having a seperate scale.