Is it a violation of Copyright Law to publicly share a video recording of a DJ playing music from his music library for a public library archive and make this available for on-demand viewing?
My favorite DJ-related story is about how "scratching" a record, as both a musical instrument and an act of composition, evolved in the hip-hop scene of the late 1970's and early 80's. It is a story of technological innovation, of community culture, and (as all good stories are) controversy. DJ's, like all contributing figures to culture, make for compelling scholarship. So I am not surprised to see this question about audio-visual content portraying a DJ on a library archive.
The short answer is: sure, it could be a violation; but there are five things that can keep it on the right side of the law—or at least mitigate the risk if there is an unintentional violation.
Here are those five "things":
Is the posted video part of a well-developed and organized collection or archive?
If "yes," go on.
Does the metadata on the unique video reflect that it is part of a well-developed and organized collection?
If "yes," go on.
Is the music part of a recording of an event, or is the music a separate track with all other ambient sound (the crowd, street noise, the DJ talking over the music) removed (or never there)?
Even if "no" go on, but have the next two really, really tight.
Has your library conducted and documented a "fair use" analysis of its posting of this particular content, and to the best of its ability, reflected accurate ownership of the item in the metadata and item information on the archive?
If “yes,” go on.
Does your library have a "notice and takedown" contact point posted on its website, so anyone who believes the content is an infringement can complain, AND has your library registered for "safe harbor" under the Digital Millennium Copyright Act?
If "yes," DJ on!
Why do I have to do the "5-step hustle" to answer what seems like a simple (if compound) question? Because how and why content is used can transform "infringing use" to non-infringing "fair use." For a component of a scholarly or historic video archive, this means being able to show that a musical recording incorporated into an audio-visual record is not merely a gratuitous use of the audio content, but rather, a critical element of a work that transcends (and doesn't simply replace) the purpose of the original.
This is, in some ways, a tall order. But if you follow steps "1" through "4" above, you significantly increase your likelihood of getting it right. And as for step 5: the DMCA has been in the news, recently, as a part of the national info-tech infrastructure that is due for an overhaul. But for now, it can protect certain kinds of service providers (like search engines, directories, and other information location tools) from liability for third-party infringement, and it is an essential part of any information database's copyright compliance toolkit.
Thank you for a good question.
 Which makes a sound like either "schkud-shckud-shzyaaa" or "hschhzka- hschhzka-zreek" depending on how you translate it into onomatopoeia, along with the skill and intent of the person doing the scratching.
 According to his tag in the Cornell University Hip-Hop Collection, scratching was invented by Grandwizzard Theodore. However, there is some assertion that Grandmaster Flash put Theodore on the path to the scratch. Either way, it is a good story.
 If you are looking for a new era to get obsessed with, early Hip-Hop is a good one. It is replete with geniuses, scandal, and triumph—and provides insight into cultural and community factors relevant to today.
 This 5-step analysis assumes your library is a not-for-profit educational institution (like a public library).
 As in: done the analysis in writing (generally a form), and retained the form.
 From 17 U.S.C. Section 504(c)(2): "...The court shall remit statutory damages in any case where an infringer believed and had reasonable grounds for believing that his or her use of the copyrighted work was a fair use under section 107, if the infringer was: (i) an employee or agent of a nonprofit educational institution, library, or archives acting within the scope of his or her employment who, or such institution, library, or archives itself, which infringed by reproducing the work in copies or phonorecords..." Of course, making video "available" can be considered a transmission under certain circumstances (like streaming), so make sure your "fair use" conclusion is solid.