Where is the auto add folder for Music?

I want to drag and drop alac files from external media to my iMac, iPhone and iPad. I expect I'll not synch the music files on these devices for a couple of reasons. (It's a secret. (In truth, too wordy.))

I gather there is a folder to which I can drag files and Music will automagically incorporate them into my library. So, pray tell, where does one find this magical folder? What path does one take to get there? For each device.

Thanks, kind Sherpas.