iTunes only lets you sync your iPhone, iPad, or iPod Touch with a single iTunes Music Library.
With iMazing, you can easily transfer music from any computer to your iPhone, iPad, or iPod Touch and preserve all metadata (e.g. artworks, ratings, play counts,…)
Anyone who wants to easily copy music from their computer to any iPhone, iPad or iPod without iTunes.
Download and install iMazing.
To import music from your Mac or PC computer to your iPhone, iPad, or iPod Touch:
Launch iMazing and connect your device.
In the left sidebar, select Music. To view your most recent music, you may need to refresh your data.
In the bottom toolbar, select Import from Folder. This will open a dialog box.
In the dialog box, select the music file(s) you want to import, then click Choose. This will start the import.
When your files are transferred, you will be notified in the Operations window.
iPhone, iPad, and iPod Touch are compatible with most audio file formats and encodings: