Edit: Actually, now that I think about it, you might have to steal it to make the copy. Your analogy is useless for this argument. Money might be an abstract concept but bills and coins aren't imaginary. Try an analogy with digital currency then maybe there be something to talk about, but I'm guessing anything you can come up with will actually be talking about "hacking" or "fraud", not "stealing".
Why bending the meaning of words?
Musicians are stiffed by the record labels, not by the fans. The fans are the ones that keep them rich, keep them popular, buy their shirts and go to their $200/seat concerts. At worst, their records are loss-leaders for an even more lucrative business.
It used to be common practice for governments to tax owners of radios (and TV sets later on). So music certainly hasn't always been freely available on the radio.
That being said, if you're sending EM waves through my property, why the hell shouldn't I be allowed tp copy them?
To further my point: not every artist is a mega-millionaire. There are countless small bands/artists where every sale counts towards them actually earning a living off of music.
it's hardly as clear cut as you are making it. if I have an apple and you take it, I no longer have the apple. if I have five apples and you take one, I have four left. it's hard to imagine you taking something from me that I will still possess afterwards in the same quantity. I would argue that the sense in which most people use "take" does not include copying.
to further my point: the law in the US, a bastion of copyright enforcement, clearly recognizes the difference between theft (a criminal offense) and copyright infringement (a civil offense). you can't go to jail for piracy.
Presumably infinite quantities of a something like an album shouldn't suggest that it's worthless. Resources have been invested into it's creation. Artists should be able to recoup some of their investment with album sales.
If it's okay to "copy" music, than the same argument can be made for every other digital product. Games, films, and essentially all software.
when i was teenager / college student i never thought piracy was wrong, mainly because of the "well i wouldn't have paid for it anyway" argument. now that i'm a software dev, i have plenty of money for music and movies and i realize that my own livelihood depends on IP protection. i can't justify it so easily anymore.