If you are using iMazing to manage your music, you will want to prevent iTunes from synching with your iPhone, iPad or iPod every time you connect it to your computer.
There are two ways to disable automatic synching in iTunes: you can disable automatic synching for all devices, or for individual devices.
To disable automatic synching for all devices (recommended):
In iTunes Preferences, uncheck Prevent iPods, iPhones and iPads from synching automatically.
Mac: iTunes > Preferences... > Devices
Windows: Edit > Preferences... > Devices
To disable automatic synching per device:
1. Connect your device to your computer and click the device button near the top left of the iTunes window.
2. In the left sidebar, select Summary.
3. In the main window, under Options, uncheck Automatically synching when this iPhone/iPad/iPod is connected.
To ensure best results using iMazing music management do not use iTunes to manage music. iTunes sync will overwrite the changes you made in iMazing.