In FFXV you have this radio you can use while exploring the world, notably starts with your car but you can get it else where too. There you can unlock songs from other FF games and play them as you desire. (mini example: https://www.youtube.com/watch?v=LnZXDyCSfbQ)
I know its not really the first time to ask for mobile orchestrion but I was a bit renewed to ask after reading the nearby SDS thread where a lot of comments talked about mount music.
In the radio I'd like to see the ability to control music stations such that you have a battle music station, perhaps FATE, exploration, and mount.
There you can create a list of songs for each type of content, and if you don't activate a station it'll perform normal behavior (lists can be stored local side).
The radio also has option for mount and exploration music to continue uninterrupted through battle, meaning it turns off the battle station and doesn't let the game play battle (or FATE) music normally - the radio has assumed control!. Could say for example an empty list means play whatever the area has set up, meanwhile if you mute a station it makes it not interrupt other stations (mute battle/fate and then they won't play through the other stations). When making a list you can choose "area music" so even if you haven't earned the song you can have it shuffle through your list.
It would be cool if SE could allow us to listen to other FF game music like FFXV allowed too. Also mount music should be listed in the radio, just the snippets the mounts themselves use (so if you own the Fenrir you can play it's song on your Fat Chocobo... if you wanted...).
Now when you first enter an area perhaps its better you don't have the radio going, to get the experience as best as SE can deliver it - so maybe SE could make a small quest in new areas to establish a radio signal in that zone. Nothing too complicated, but it might be a good idea to properly show off a region before allowing the player to tweak it.
Personally I'd be turning off open world FATE/Combat music because when I just start to get into a nice area song a monster or FATE decides to cut it abruptly (it's annoying, imo). Would like to make my own mount playlist, but I quite like most area's natural sounds so I probably wouldn't use exploration station.