Groups like Public Enemy pushed technological and creative boundaries to the limit, crafting elaborate collages that might layer dozens of nearly unrecognizable aural quotations over the course of one song. As we document in our film, the sample clearance system that emerged in the early 1990s put the brakes on this type of music making. Chuck D once told me that a Public Enemy song that contained 20 short samples would more or less cost 20 times what it would take to sample a single chorus of someone else's song.

Why? The music industry believed that the law didn't distinguish between copying one second or half a minute of a sound recording. Therefore, record companies now insist that every fragment of sound needs to be cleared, something that fundamentally altered the aural evolution of hip-hop music. The more complex you make your sound collage, the more impossible it is to share with the world. And in the course of documenting the legal and cultural history of this art form, Ben and I are risking being sued.

One of the more headache-inducing aspects of the way copyright law is interpreted is how haphazardly it is applied in different contexts. When writing a book, quoting another book is perfectly acceptable, but quoting more than two lines from song lyrics (even if it takes less than 0.001 percent of the book's total text) might give you and your publisher a problem. If your band perfectly imitates a distinctive drum rhythm from a Bo Diddley record, no worries, musicians have been doing that for half a century. But when you sample Diddley's beat it could be a copyright infringement if you don't get permission. Inversely, you don't need approval when you record a cover of someone else's song, as long as you pay the per-song fee that is set by Congress and don't alter the lyrics. It gets really confusing.

Copyright Criminals from IndiePix on Vimeo.

When sampling, one has to deal with two types of copyright holders: the song publishing company that controls the composition (the lyrics and melody) and the record company that owns the sound recording (in other words, the recorded performance of the musical composition). Each copyright can be expensive to clear, and the costs multiply exponentially if a song contains several samples. You sometimes end up paying 200 percent, 500 percent, or even 2,000 percent of what it costs to simply record a cover of someone else's song. Sure, original creators should share in profits when it is appropriate, but each share ought to be a fraction of what the new work generates.

Northwestern University Law Professor Peter DiCola and I demonstrate this problem in a forthcoming book titled Creative License (out in early 2011 on Duke University Press). We asked what would it would cost at today's rates to clear the audio fragments that make up Public Enemy's classic 1990 album Fear of a Black Planet. We crunched the numbers, and in our conservative estimate the group would lose roughly five dollars per album. That's a loss of five million dollars on a platinum record!