You have put your finger on the a very difficukt question Les...I think that you can't always make that assumption, you need to weigh up a lot of evidence. I think Nicholas Blundell's pal was a bagpiper, put it that way.(It is 30 years since I did that research, it woild take me a while to revisit that stuff and go through the evidence!).
   A good question to ask is "If this reference to a piper does not refer to bagpiper, what else is it likely to refer to?". Clearly it might in some contexts mean spmething else...penny whistler? Flautist? It needs careful consideration.