A video mashup (also written as video mash-up) combines multiple pre-existing video sources with no discernible relation with each other into a unified video. These are derivative works as defined by the United States Copyright Act , and as such, may find protection from copyright claims under the doctrine of fair use. Examples of mashup videos include movie trailer remixes, vids, YouTube Poop, and supercuts. The first type is a derivative music video, which is the most common one, by recombining two or more pre–existing materials together into a new one. These materials usually are prevailing music videos, but also includes separate songs, videos, and still images. According to Navas, it can be a regressive type, for its promotional purpose. The second type is slightly different from the first. It allows the users record their own track – either sung or played on an instrument – and then combine it with other tracks from internet together. These two types of music video mashup are usually edited to match the rhythm of the song, and seeking to show a particular aesthetic style towards a celebrative communication. The third one is a music video created from bits and pieces from various YouTube performances clipped. It is now a widespread or traditional type, which stresses the participant feature of remix culture. According to the clarification of mashup by Navas, it could be the reflexive mashup, for it beyond the limitation of common music video, and eliminate the distance in geography and nationalities. The last two types are typical use-generated contents in the age of Web2.0,which reflects the more participation in mashup or remix culture. Political video mashups are a primary example of citizen-generated content. These mashups allow the creator to form new meanings by juxtaposing two pieces of original source material; for example, someone may take footage of a politician's speech and 'mash it up' with footage from a popular reality television show. This form of mashup, according to Richard L.