Interconnects: solid or hollow core wire?

Well, yes, it's solid. We surely could include the category, although it's not what originally I had in mind.

What do you have in mind?

I've expanded my mind.

So now it's "Expanded Core?" Most of my cables, according to the mfgr description, are "soft core". "Hard core" cables are tawdry. Note that silver plated carrots can be used as "veggie core" and plated animal parts strung together are "meat core". Avoid "molten core" as they can burn a hole in your rug.

I've experienced the most emotional connection to music in my home with solid core wire. DNM, Crimson. Those cables beat out the Kimber Select, and Nordost Tyrs that I USED to use.