I dont know which wireless system you want to use. A hard disc with wifi is already a NAS, may it be a simple one. For a friend I installed a Western Digital My book 7 years ago and it still runs perfectly.
First you might want to check if your Mac music files play on Rune, as well as the formatting of the wireless drive, which has to be compatible with Mac and Rune. For this friend I installed Tuxera on his Mac for complete drive compatibility
https://ntfsformac.tuxera.com/.