The effects of humidity changes on natural gut harp strings

Natural gut harp strings are notoriously sensitive to changes in humidity, but the nature of this sensitivity is poorly understood. The results of some recent measurements are presented, in which a number of well-settled strings were held at constant temperature and subjected to changes in humidity. The results show multiple periods when, after raising the humidity, the strings appeared to undergo additional periods of creep. When the strings were not creeping, there appeared to be some form of coupling between humidity-induced changes in the string linear density and its tension. Moreover, the effects of these changes in linear density and tension largely cancelled out, with little net effect on the string frequency. The results presented here seem to indicate that the useful life of a gut harp string may be determined as much by its propensity to creep as by its inherent yield strength.