Just wanted to let you know about some changes:
We got a cease and desist letter about musical copyright infringement on the site from the good people at the NMPA (National Music Publishers' Association), so a bunch of lessons had to be taken down.
To refresh everyone's memory about what's not acceptable, published songs not in the public domain are protected by copyright and only its authors or those who have been granted permission by the author can create alternative versions of these songs.
Thus, if you want to make a lesson based upon copyrighted material, then you must get permission of the author. It isn't enough to put your own spin on known material, as derivative works are also covered under copyright, so these also need the permission of the author to be published.
Otherwise, don't use copyrighted material as the basis for a lesson. Many songs use the same chord progression or the same style, so you can easily teach a lesson about how to play in a specific style on a specific progression without citing a known song as an example of that progression or style.
The sordid details:
Lesson Authoring Guidelines
Member Agreement