I used to buy wound harp strings from Robbie Robinson in Mt. Laguna California. He sold plans for a machine to make wrapped harp strings--which had a solid core and a wrapping---same as any wound string is made--- different wrappings maybe and different lengths, but made the same way. I understand that Mr. Robinson is no longer making strings but it seems to me that Betty Truitt of Mt. Laguna took over his business( seems she did business as "Dragon Whispers") and she may have copies of that "string machine". As I remember, it was a fairly easy machine to make-- it had two live centers( as on a lathe) and the apparatus could easily be attached to the studs (in the walls) in your workshop---. The core material was attached to the live centers, and the winding was applied and tied off by hand-- one string at a time. I may( probably) still have the plans-- if you don't have any luck locating her, I'll see if I can locate them--