Drum machines are a piece of portable music equipment that reproduce drum beats and drum rolls. Drum machines are a popular form of sound equipment with musicians such as guitar players and bassists because they can stand in for a live drummer. This helps the musician practice alone and improve their ability to keep a steady tempo. Drum machines are also a useful piece of audio equipment for songwriting; as drum machines can be recorded in a studio and are found on many demos. Many popular forms of music, such as rap, hip hop and dance music, use drum machines on finished recordings because of their ability to produce fast beats which a live drummer would have difficulty playing. More than a few rock musicians are opposed to drum machines; stating that the sound of an electronic drum isn’t natural and lacks the emotion of a live drummer. Professional drum machines are able to accurately reproduce the beats and rhythms of many styles of music such as jazz, alternative, heavy metal and reggae. These drum machines are also able to change tempo and include drum rolls with the use of a footswitch while the musician plays other instruments such as guitar or piano. Drum machines are available as stand alone equipment or they can also be found as part of electronic keyboards and computers. Popular artists who use drum machines in their recordings include Nine Inch Nails, Filter and Static X. Many artists will use drum machines in their home studios to record demos of songs, also called sketch pads, to give other members of their band an idea how a song will sound.