Re: Forza Horizon 3 (XboxOne/W10, play anywhere) - Sep 27, 2016, mate!
You need to have OneDrive, Groove Music, and a working Internet connection to do this, but you don't need to pay for anything unless you want more space on OneDrive.
I did all of this using Windows 10. Under OneDrive, there's a folder for your music. Add some music to it. Then open up GrooveMusic and create a playlist, for example, "My Forza Music." Add the music from your OneDrive to your newly created playlist. When you pop in Forza Horizon 3, go to settings > audio > Groove Music playlist and change it to "My Forza Music." When driving, set your radio to "Groove Music." If you want to change songs, just exit and go back to "Groove Music." The songs will play in the order found on the playlist, or you can set it to shuffle in Forza's settings.
If done correctly, you'll be able to listen to the music you added to your playlist. You can add the first 5 GB of music for free; if you want more space for your OneDrive, you got to pay. There are some songs I added that wouldn't play for some reason, but it's not a big deal. Listening to Prince and Talking Heads on the road is fun.
Please let me know if you have any questions or if I'm unclear about this. Perhaps I wasn't paying attention, but I don't think there's any indication in Forza that tells you that you could do this.
Wii U / 3DS Network ID: eric.n128
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