How does one download newly added music stored in my Apple/Itunes library to my ancient old Ipod?d

See Sync your iPhone, iPad, or iPod using your computer - Apple Support. iTunes on Windows computer, or Mac up to macOS 10.14 Mojave. In macOS 10.15 Catalina or later iTunes is replaced by Music and sync duties are incorporated in the Finder app.

Note that you cannot sync content that is in the cloud or comes from the Apple Music subscription service.

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You use iTunes, or Finder on Macs running macOS 10.15 Catalina or later.

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