The arrival of Grandmaster Flash at Mosaic on Friday will mark a rare opportunity for the city's music fans to enjoy a hip-hop pioneer in the flesh and on the wheels of steel. It will also mark the first opportunity for the Power & Light District to welcome with open arms a hip-hop act after the debacle surrounding DJ Jazzy Jeff. For those who don't remember, DJ Jazzy Jeff left the KC Live! stage mid-set on a Saturday night in June, generating immediate crowd confusion and weeks of media fallout. Regardless of what transpires during his performance, it's unlikely that Flash will be surprised. Spinning and mixing since disco was still in vogue, the Barbados-born and Bronx-raised DJ has seen it all: from the unexpected explosion of hip-hop in the 1980s (which he helped engineer) to a famous beef with collaborator Melle Mel to, more recently, his inclusion in the video game DJ Hero and the release of The Bridge, his first major studio album in more than 20 years. Flash is indeed a rarity: an unparalleled veteran of the game that he himself helped create.