There is never just one chord that can go with a particular phrase of music. If there was some standard way of working it out, then I think we would end up with a lot of very boring music. Personally, I just mess around with a few of the most obvious chords (and a few less obvious ones) till I hit the sound I want. I like to sing harmany with songs, so that often makes it easier, as you have 2 notes to work with instead of one.Bagpuss