Use the new Audio Mix feature on the iPhone 16 series or spend some money on an external microphone (or wind screen). While iPhones excel at recording excellent quality video in glorious 4K HDR ...
Shooting video and recording music at the same time is a nice concept, but in practice it's not great.
iOS 18 has brought many exciting features to the iPhone ... playing as you record, and if it’s coming through the speaker, the microphone will capture it alongside your video.