How do I transfer my Music to another Mac…

… with the music files on an external drive.

I'm a lifelong chorister and have been collecting music on my Mac for the best part of 20 years, first in iTunes and now in Music – 30,000 items which use almost 2Tb of disk space. The items include CD albums, live concerts [captured from various sources] and professional recordings of concerts and recitals in which I was a performer or producer. So it's more than entertainment – it's my life.

All this is on my desktop iMac, with the music files stored on an external USB drive. I playout through headphones or a budget amp & speakers in the study.

Now, however, I want to move the whole lot to another iMac in the living room, which is connected directly to my hifi.

Presumably I start by moving the USB drive, but what about the 'working files' / library etc? Most of the official / semi advice online seems to assume that the content is in the default locations on my internal HD.

Can a kind person please provide / point me to a step-by-step guide on what to do / how to do it? I'm reasonably knowledgeable about Macs, but I'm more than a little confused about this and don't want to risk losing anything.

TIA

Ken in Liverpool