It's parody now, baby!
Nixon Peabody lawyers know that this is a permitted use of their copyrighted song, applying the doctrine of "fair use" as described in the law firm's published Copyright & Internet Law Glossary.
The doctrine that permits use of copyrighted material without obtaining permission from the copyright owner. §107 of the Copyright Act contains a list of the various purposes for which the reproduction of a particular work may be considered "fair," such as criticism, comment, news reporting, teaching, scholarship, and research. §107 also outlines four factors that are considered to determine fair use:
1. the purpose and character of the use, including whether such use is of commercial nature or is for nonprofit educational purposes;
2. the nature of the copyrighted work;
3. amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
4. the effect of the use upon the potential market for or value of the copyrighted work.
"The idea of copyright law is that, after a time, every work comes back into the hands of the public, where it can be reused, recycled, and made part of new creativity without the artist having to pay a fee or call in the lawyers. Yet some copyright holders act as though copyright is both permanent and boundless, pressing claims that threaten even traditionally protected activities like making a parody. These claims strip-mine the public domain, robbing the next generation of artists of rich source materials for creativity." ~EFF