Zany strings and finicky banjo bridges
David Politzer · CaltechAUTHORS (California Institute of Technology) · 2014
Basic physics offers some clues about why a given banjo bridge’s sound depends strongly on its tiniest and most subtle details. The strings present the bridge with sets of independent vibrations, with members of each set having nearly the same frequency. When there are at least two separate vibrations with the same frequency, any interaction between the two can have a substantial impact, no matter how weak that interaction. The bridge provides that interaction, allowing strings to talk to each other (and themselves), swapping energy back and forth during the time of a single pluck, all having a discernible impact on tone. This analysis does not predict anything about real bridges, nor give hints how to make “better” ones. However, it does offer some perspective on real banjo sound and how strings actually wiggle.