According to the United States copyright law, "fair use" allows creators to incorporate copyrighted materials into their own work - without obtaining the permission of the copyright owner -when certain conditions are met.
Fair use recognizes that while the primary purpose of copyright laws is to encourage artistic and cultural innovation, rigid application of copyrights would actually stifle that creativity. Society benefits when creators have the freedom to critique and comment on the works of their peers, or to remix and reuse artistic material in new and inventive ways.
That's why creators should understand the concepts behind fair use based on the "four factors", that are:
Copyrighted materials in the videos on Dance2sense Services are used under fair use, because the main goal of Dance2sense is educational purposes and that completely suites to the "four factors".
D2S strongly believes that using music as the background song of video is fair use, particularly if it just enhances understanding dance moves of the video. Dancers create something wholly new and unique, that's why the value is not the song, but the choreography. Therefore creators may have strong claim to fair use.