It seems the music industry is trying to shut down their fans again. The National Music Publishers Association has sent a letter to the guitartabs.com site asking them to stop distributing guitar tablature. Guitar Tabs is a site where users can download tab files; I understand that generally these files are written by people who listen to a song, work out the notes on a guitar, then submit it to guitartabs.com for others to enjoy. Unfortunately for the music fans, this activity violates copyright law.
Copyright law, at least in Canada (I have read the Copyright Act, but IANAL) specifically defines things like making guitar tab as making a copy. Copyright doesn't depend on the means of reproduction; even if the new work is different but very similar to the original work, and is derived from the original work, it doesn't excuse the copyright obligations of the "copier". If you read a novel, and write it out by hand, you are not allowed to distribute that copy, even if you make spelling mistakes or re-word a few sentences. Heck, you are not even allowed to translate a work into another language. You are not allowed to make a movie out of a copyrighted book nor sing a song with a similar tune as another song, even if you change the lyrics. To my knowledge these basic rules are in all copyright laws passed in any countries that signed the Berne Convention.
Some people confuse the issue further when they consider the copyright of the author of the derived work. The derived work may be subject to the "copier's" copyright as well; consider a translation of one book into another language: The author of the original book owns the copyright for that book, but not the copyright for the translated book (assuming it was translated without authorization of the author). The copyright for the translation rests with the translator, however, since it is derived from a copyrighted work, the translator can not distribute it without permission from the original author. The author does not have permission to dictate when the translation will be distributed; the author can only dictate when it will NOT be distributed. When the copyright of the original work expires, the translator is free to distribute his work, and the this version of the work enjoys full copyright protection. Similarly, the authors of the guitar tablature can prevent others from copying their work, however the artists who wrote the songs in question (or, whoever owns the copyright) can prevent the distribution of tab.
Should the NMPA stop guitartabs.com from distributing tabs? Well, the NMPA makes their money selling sheet music and tab. Under copyright law they hold the keys to this particular source of revenue, and a site like guitartabs.com presumably prevents them from making money on certain tab sheets. If you believe in copyright, then it follows that guitartabs is blatantly denying the NMPA of its due revenue. Sorry tab fans.
Note: This post is meant to explain copyright law. It is not meant as an endorsement or condemnation of this law.