[Harp-L] Key centre

[martin oldsberg <martinoldsberg@xxxxxxxxx>]

Bill wrote on another matter: "But then I talked to one of the tutors about it and he said but you hear the key centres ..." 
 
 Key centre: I may have a rough notion of what it means, but sometimes rough notions are just wrong.
  Is there anybody out there willing to explicate a bit on this concept?
asks,
Martin