iTunes sells inaudible tracks for the same price as regular songs.
I found this to be pretty interesting.
Quote:
Apple treats the silent songs just like their more musical counterparts. The silent tracks sell for the same 99 cents as other songs, feature free 30-second "previews" and are all wrapped in Apple's usual digital-rights management software to prevent unauthorized copying.
Even more humorously, three of the tracks--all titled "Silent" and all by hip-hop group Slum Village--are labeled as explicit, even though there is only silence. For those who worry that the lack of sound will be too racy, iTunes offers "clean versions" as well.
The mention of John Cage's "4'33"" is interesting as well.