How to copy (not transfer) iTunes library from Mac1 to Mac2?

All articles  have seen refer to 'Transfer' iTunes library from Mac 1 to Mac2 - I want to copy so Mac 2 iTunes begins life as new base for music which can be updated independently of Mac1.

Quite by accident, I discovered that an iTunes library could be used on another Mac as long as source Mac was still on local network. This is not what I want.

Again, how do I copy (leaving source library available independently) from Mac1 to Mac2. I would expect both instances of iTunes library to be independently updated.