In the olden days when I was a youngin' (God, I sound old!) I saw fellers loosen their strings & shove a yellow pencil under the strings right next to the nut, retune it & set in a twangin'. The yellow pencil tends to work better than a round one cause it has flat sides on it & will usually stay put. I knew a carpenter who used a 3 sided carpenter's pencil that way, too. He put grooves in the top pointy edge for each of the strings. Talk about groovey!