Sync iTunes to multiple computers.

You can't really "sync" as such. For individual items on the same network you can look into Home Sharing:

Use Home Sharing to share iTunes content with other devices - Apple Support - https://support.apple.com/HT202190 - "Share and stream content from your computer’s iTunes library to other computers, iOS devices, and Apple TVs. Use Home Sharing with up to five computers on your home network"

Share your iTunes library over your home network - Apple Support - https://support.apple.com/HT201779 - about Music Sharing and Home Sharing

Home Sharing Support page - http://www.apple.com/support/homesharing/

iTunes 12 for Mac: Use Home Sharing to import items from another iTunes library - https://support.apple.com/kb/PH19614

iTunes: Setting up Home Sharing on your computer - http://support.apple.com/kb/HT4620

Alternatively you can just replace one library with another, or install it alongside one that already exists on a ocmputer (but only use one at a time):

Apple's 6 pages of exhaustively meticulous step-by-step instructions: How to move your iTunes library to a new computer - https://support.apple.com/HT204318 Use this if you suspect any of your media are not in the standard location (iTunes Media folder).

My one-sentence summary if you always use iTunes' default preferences settings: Copy the entire iTunes folder (and in doing so all its sub-folders and files) intact to the other drive, hold down the option/alt key (shift on Windows) while starting iTunes, and when requested to select a library select the iTunes Library.itl file in the copied folder (Open a different iTunes Library file or create a new one - https://support.apple.com/HT201596).

Sure, but it works best if you your "sync" is one way. Just use rsync on the command line or any of many folder sync products. There many free and paid folder sync products.

It's best to designate one of the libraries as the main library. If you sync from the main to the secondary, whatever changes you make in the main library will sync to the secondary. Any changes in the secondary library are lost.

I sync my iTunes library to my unlimited google drive using Google Back up and Sync. I then use RClone to to occasionally sync it down to my work computer.

Make sure iTunes isn't running on the secondary computer when you sync.

James,

You could also consider iTunes Match: Subscribe to iTunes Match - Apple Support

Cheers