With this cassette adapter, you can use the tape player in the Goldwing's built-in music system to listen to music from MP3, iPod, iPhone and the like, or listen to your GPS, as well as its optional MP3 player directly in your speakers or intercom.
The cassette is inserted into the cassette player, just like a regular cassette tape. Then connect it to the selected device with the mini jack, and the sound will be heard in the speakers or the intercoms.

This is definitely the cheapest solution if you want to hear another radio on your Goldwing.