DVJ discs, as noted above, are DVDs containing one or more music videos the performer wishes to play. The music and video contained on the disc can be anything the performer desires, but as with standard DJs, the most popular genres are the various forms of electronica. In addition to the audio, which is sent to a sound system like other player systems, the video component is output to a video projector or other visual display. The audio and video for the disc are then always in synch regardless of any scratching, mixing, and other transformations the performer does on the media. This was a huge improvement over any previously possible method of performing with audio and video together, as the performance often had to be very meticulously planned so that the video being displayed matched the audio. This sometimes required a second performer to handle video playback, leaving little room for improvisation by the DJ.