Developers use these for testing or for installing the standard Apple Music app on devices that can't access the App Store directly.
Q: Will I get updates for the Apple Music IPA? A: No, IPA files may not receive updates or bug fixes like the official app. You may need to reinstall the IPA file or update it manually. Apple Music Ipa Download
A common desktop tool for Windows/macOS that signs and installs IPAs using your Apple ID. Developers use these for testing or for installing