Music Player

Not exactly, there does exist a song data converter to change FF5 song data into FF6, a japanese tool called FF5>FF6 MCS2. I'm not sure we have it hosted here, I thought so but it seems not. Besides that, you can directly inject some CT songs over to FF6, since they share a very similar structure, or music engine/core. But not all of them due to a drum command that FF6 lacks. Same with Romancing Saga 3, can inject over some songs. Besides this you might be thinking of RS3ExTool2? This is the tool used to convert MML data to song data that FF6 can use. It doesn't do everything though, just that. There's a tutorial I made about how to use it though, if you're interested in learning. This method you can get any song ever as long as it meets the requirements:
https://www.ff6hacking.com/forums/showth...l+tutorial

But no, no tool that can place in other FF game's songs. And sadly no, there is no mysterious girl song data for download as of yet. These are the ones available thus far:
https://www.ff6hacking.com/forums/showth...p?tid=2558