The performance of musical instrument strings is improved by treating the strings with a polymer vapor, avoiding problems common with spray type polymer coatings, extruded or laminate coatings or wipe-on liquid coatings, including heat damage, imprecise dimensional control, possible flaking, peeling or easy removal of the coating or adverse changes or damping of the musical qualities of the strings. The treatment may be applied either to the core of said strings, to strands wrapped around the core, or both. The treatment may be applied either before or after wrapping said strands around said core.