Music changes how you film. You move differently, you talk differently, you're more yourself. For two years I filmed almost every video with a song playing behind me.
When I lost access to the app I used, I tried replacing it. The wide cameras I tried stopped my music when I pressed record. The ones that kept the music playing didn't give me a wide front view. That gap is the whole reason this app exists.
Getting it right is harder than it sounds: the phone has to share audio between apps, record your voice, keep the music going, and not turn the whole thing into an echo. Some of that has passed early testing on my iPhone. Some is still being tested. I'll keep saying which is which.