Mixtapes are now commonly used by labels and new artists as a promotional tool, as a way of generating hype. An unsigned artist might release several mixtapes to generate buzz, leading to interest from record labels, while a signed artist may release a mixtape to promote a future studio album, in a sales model relying on word of mouth to increase the artist's credibility (known as "street cred"). Often each track on a promotional hip hop mixtape will feature the same artist, thus making it more difficult to differentiate from a standard album. However, these mixtapes will usually have much lower production values than a studio album (such as containing demos or rough cuts of the tracks), and contain numerous collaborations, remixes, freestyles and voice-overs, often arranged in a specific flowing fashion. It's common for such mixtapes to re-use previously heard instrumental tracks from other artists.