Hearing that probable Aussie on 531 with the stock T-615 is really cool!
I checked the Grayland Master logs (skillfully compiled and maintained by Chuck Hutton) as well as my own logs for 531. The Australian most often heard on 531 has been 2PM Kempsey in New South Wales, but there was one log by Walt Salmaniw of 4KZ Innisfail.
I had a log of 2PM in 2oo5, with a slogan of "Easy Listening 531".
If the music you noted was "island" music or Maori style, it would almost certainly have been 1XPI Auckland, NZ.
Congrats again on the fine Ultralight catch!
Puyallup, WA USA