I seem to have missed something, my ageing memory seems to tell me that the original questioner was speaking of a single play rather than a troupe of musical reenactors. If that is the case it would seem that a lutar, strung as a guitar, would be the appropriate instrument. It would be a bit much to ask the performer to learn the lute, and if it is a play rather than a musical ensemble a few note should do. It does depend on the purpose, if they are putting on Hamlet then "the play's the thing" and the instrumental is periferal.
Best, Jon
