According to Ars Technica, if you bought your music, uploaded it to YouTube Music, you don't own the music and if you own a Google Home smart speaker or any other Google Cast device you'll need to pay a monthly fee to cast to your speaker once Google Music shuts down.
So this is new. You might buy your music, and buy the speaker but now you have to pay for the rights to use it.
YouTube Music is really only for The Music Renter—someone who wants to pay $10 per month, every month for "Music Premium." This fee is to buy a monthly streaming license for music you do not own.
The problem is YouTube Music also locks regular music-playback features behind this monthly rental fee, even for music you've uploaded to the service.
"I've paid hundreds of dollars for Google Home speakers, which (for the normal "medium" size) are $130 a pop. Thanks to the initial slow rollout of basic features to a Google Home, for a long time, music playback across multiple speakers was the only thing a Google Home could do well. When people purchased these speakers, Google Music was the official way to play your music on a Google Home, and of course, it did so without a monthly fee. When Google shuts down Google Music, Google will be taking its line of speakers and telling customers "If you want to continue playing music on your speakers, start paying a monthly fee", moaned Ars.