How to access files on android for music player

Copy outside the owncloud store means double the data. Im pissed because we are loosing functionality and freedom every day, sometimes for acceptable reasons, sometimes simply for greed. On a smartphone specially this is scary. No useful stock or free tools means you are nudged into walled gardens to use a tool you have paid much money, i am hard in favour of opensource, but im not a developer.
Thats a bit frustrating