On June 30th, I did a post on the question of fixation and derivative works. Whether Fred von Lohmann could be stopped from singing in the shower by the derivative right (assuming an altered version, intentionally or not) even though it would be a private performance, was an unsolved question. The post mostly explored the difference between reproduction right (which requires fixation in copies or phonorecords) and the derivative right (which doesn't).
There is another difference between the two rights, though, namely, violation of the derivative right can occur not just by copying, but also by adding to the original. I use the term original here is the sense both of the intangible work and an intangible fixation: the reproduction right isn't violated if Marcel DuChamp painted a mustache on your physical painting, but the derivative right might be. Judge Posner wrote, in a case involving the addition of teletext to cable retransmissions, that "if the publisher of a book leaves the inside cover blank, the book seller cannot inscribe the Lord's Prayer on them in order to broaden the book's appeal," WGN Continental Broadcasting Co. v. United Video, Inc., 693 F.2d 622 (7th Cir. 1982). This is similar to a real such case, National Bank of Commerce v. Shaklee Corp., 503 F. Supp. 533 (W.D. Tex. 1980), where advertisements were affixed to to the copyrighted work. In a more recent case, National Conference of Bar Examiners v. Sacuzzo, 2003 WL 2146772, at *2 (S.D. Cal. June 10, 2003), infringement of the derivative right was found when student's recollections of taking secure tests was added to copyrighted material.
All of these cases are interesting because infringement was based not on copying the original, but adding to it. And there of course there are the subtraction cases, like Gilliam v. ABC, 538 F.2d 14 (2d Cir. 1976). Whether less is more, as Mies thought, or a bore as Robert Venturi thought, infringement can involve more or less.