how do I transfer playlists from a MAC to a PC?

See Make a split library portable. Transferring a portable library between platforms is fairly easy. Use a network to avoid file system issues with external drives. If you only want to copy one or more playlists you have to make sure that the media is also copied in a similar layout, and edit the paths to each track to match the new system before importing. XML playlists carry the most detail between systems.

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