Hello!
On Android 7.1, I could save music by subscribing to a memory card. After updating to version 8 - I can not save anymore.
I tried to format the card, I used another card, deleted the application and cleared the cache.
In this case, the music that I upload through the PC to the memory card - the application Play Musiс sees correctly and played.
Technical support Google informed me that it did not remove such an opportunity, and support from Sony does not understand what is going on and advises trivial things, up to instructions on transferring data from phone to memory card. In the end, they just said they were not responsible for third-party applications.
It's funny, considering that it's an application from Google and a number of part of the android system.