>I notice the links I've read talk about "mechanical" royalties. Does this refer to tangible recordings on to CDs etc.?

That'd be player piano tapes and similar or derived media :).

>I'm wondering about live performances. Suppose you sell 10,000 tickets at an arena, and you cover a song once during the show. Does that mean you owe the songwriter 9.1 cents? < g >

Imagine how much you owe for all the songs left out there in the cold, uncovered?

BTW, why is there a special designation of "cover song"... sheesh, 99% of the classic music performers do them all the time, and never, for all the centuries they did that, bothered to have a special name for "I'm playing a song I did not write and somebody else played it before me".