There was a fellow at the S.C.A's annual Pensic War, playing a goatskin (with the fur still on!) bagpipe with one drone. I didn't like it as much as Wolgemut's pipes, or the fine Highland piper at the Mountain Confederation's bagpiping contest. (If that man's name wasn't MacCrimmon, it should have been!) But it was interesting. His had a blowpipe and chanter. I didn't get a chance to ask about country of origin.
Re. Shelta, I grew up in Squirrel Hill, a Jewish neighborhood. A lot of the older people spoke Yiddish. In a way it was a "secret language", sometimes spoken to conceal things from gentiles, or from children who didn't speak the language. But there are dictionaries. There's a very rich Yiddish literary tradition. French was a "secret language" among wealthy Victorians, used to conceal things from children and servants. "Secret language" is in the ear of the beholder.