An improved musical instrument string is provided The string includes a polymer cover that protects the string, from contamination while maintaining the original "lively" sound of the musical string. By supplying the cover over a conventional string and preferable over a conventional wound string, the string is protected against contamination while also making the string easier to play. The preferred cover comprises at least one layer of expanded polytetrafluoroethylene (ePTFE) that is most preferably sealed with a polymer coating. In particularly preferred embodiments, a cover is applied over a portion of the length of the string having a relatively reduced variable mass. The result is that the string has relatively uniform mass along its entire length thereby assuring correct intonation.