Sorry Todd, but this is a very well-established part of copyright law. There are many kinds of copies, and copies need not be exact. It is quite easy to unintentionally breach copyright. But if someone set out to make a copy, no matter how imperfect the result, you are definitely violating copyright.
To name an important example, it is not exactly copying to make a translation. Yet translations are still covered under the original copyright. (The translator also gets a copyright, recognizing that the resulting document is partly copied, and partly created.)
That case is very similar to this one. Someone sets out to wind up with a work that is in some way the original, but which is very different in detail. (In one case it is sound vs writing, in the other it is one language versus another.) The result, no matter how different, is covered under copyright.
IANAL and all that, but I think you'd be hard-pressed to find a lawyer who would disagree.
Cheers,
Ben