Music library not syncing

Hi LLLUUUNNN,

Thanks for reaching out to Apple Support Communities.

It sounds like you're having an issue syncing music from your Mac to your iPhone.

We're happy to assist.

We recommend checking out the steps in the section titled "Sync music to your device" from the article here: Sync music between your Mac and iPhone, iPad, or iPod touch

1. Connect your device to your Mac.

You can connect your device using a USB or USB-C cable or using a Wi-Fi connection. See Sync content between your Mac and iPhone, iPad, or iPod touch over Wi-Fi.

2. In the Finder  on your Mac, select the device in the Finder sidebar.

If you connect your device to your Mac using a USB cable and don’t see the device in the Finder sidebar, see If your device doesn’t appear in the sidebar. 

3. Click Music in the button bar.

4. Select the “Sync music onto [device name]” checkbox to turn on syncing of your music.

With the checkbox selected, syncing is set to transfer all your music to your device. 

5. To sync a selection of music, click “Selected playlist, artists, albums, and genres.”

6. Select the checkbox for each item you want to sync in the music list. Deselect the checkbox for any item you don’t want to sync.

Click Artists, Albums, Genres, or Playlists to see your content organized by that category. 

7. Select syncing options: 

* Select the “Include videos” checkbox to include videos when syncing.

* Select the “Include voice memos” checkbox to include voice memos when syncing

* Select the “Automatically fill free space with songs” checkbox to have your Mac fill the free space on your device with songs when syncing. Use this option if you have a large music library on your Mac but don’t have room to sync all of your music to your device. This option syncs as many songs as possible.

8. When you’re ready to sync, click Apply.

You can choose to sync your Mac and your device automatically whenever you connect them. See Turn automatic syncing on or off on Mac.

Before disconnecting your device from your Mac, click the Eject button  in the Finder sidebar.

We’re recommending the steps above because they directly address the issue you initially posted about: songs are not syncing from your Mac to your iPhone.

Please let us know the outcome after giving the above steps a try.

Cheers!