On June 27, 2019 Square Enix stated that they had updated the PlayStation 4 version of Final Fantasy IX "so background music will not restart after every battle or Tetra Master match."
A few weeks after they released similar updates for the Switch and Android versions of Final Fantasy IX (but only on Google Play) and each of these announcements were met with a lot of positive praise from fans.
We've heard your feedback, and have patched #FinalFantasy IX on #PS4 (version 1.02) so background music will not restart after every battle or Tetra Master match.— FINAL FANTASY (@FinalFantasy) June 27, 2019
We can also confirm that we're working to fix this issue on #NintendoSwitch, #Xbox One, #Windows 10 and #Steam. pic.twitter.com/Oq3zPNEzxv
At the same time as publishing these fixes, Square Enix also stated that they were still working to fix the issue on iOS, Xbox One and PC. But fast forward almost a year and nothing has happened. The Xbox One, PC, and iOS versions of the game have not been updated and there's no timeline for when the fix might appear.
For consumers who have purchased those versions, this will no doubt be frustrating. Square Enix made a commitment to fix this particular issues and thus far, as has not followed through.
Fingers crossed we will hear something from them soon in this regard.