When mixing vinyl records or CDs, DJs often use volume levels to transition music in and out of a mix. A crossfader uses a horizontal slider to raise and lower the volume of two separate tracks. As the volume level of one track increases, the second track is made quieter. Positioning the slider in the middle position allows both tracks to play at their actual volume settings. Moving the slider completely to one side mutes the track on the opposite end.
Numark's CD mixers allow users to adjust the volume levels of low-, mid- and high-range frequencies within an individual track. This feature is especially useful if you are attempting to isolate vocals or drums for mixing purposes. Many DJs create remixes of popular tracks using these methods.
DJs often use headphones to prepare the next track within a mix for playback while the previous song is still playing. Numark's CD mixers are equipped with a headphone jack and dedicated volume control. By pressing "Cue" next to the channel's volume slider, the music produced by that channel will play exclusively in the headphones.