Have you checked your App Library to see if the Music app is still there?
(It may be that only the App icon was deleted from the home page.)
How to use the App Library to find the app:
Organize the Home Screen and App Library on your iPhone - Apple Support
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To restore a built-in app that you deleted
(Delete built-in Apple apps from your iPhone, iPad, or Apple Watch - Apple Support)
- On your iPhone, iPad, or Apple Watch, go to the App Store.
- Search for the app. Make sure that you use the exact name of the app.
- Tap the Redownload button
. - Wait for the app to restore, then open it from your Home Screen.
If you have Apple Watch, restoring an app to your iPhone also restores that app to your Apple Watch.
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If Apple's method isn't working for you, you may want to send feedback to Apple:
Product Feedback - Apple
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Trouble-shooting: How to: Redownload apps and games from Apple - Apple Support. and .... What to do if you can't redownload the app.
If you need to re-download purchased music after redownloading the app, try the steps in this article: Redownload music - Apple Support