If you can your best bet is loading your music on your mobile or use spotify or similar, buy a bluetooth FM transmitter for £15 and bluetooth all your music and radio stations to your Harmony unit.
Check this :
https://www.ebay.co.uk/itm/Baseus-Wi...wAAOSw5eBfVZxc
These are so good these days you get no feedback or hiss from FM transmitters