chamade

A "chamade" is, according to Webster's 1913, "A signal made for a parley by beat of a drum."

But that's not all!

No, indeed!

For MW3 and Webster's 1828 add that it may instead be a trumpet signal for a parley!

"Chamade," you are indeed a versatile and many-faceted word.

However, I have not yet discovered what word to use in the case of a kazoo signal for a parley.