hype man
n.— «Hammer and the Posse, a group consisting of four dancers, two DJs and one “hype man” (“He’s the guy who pumps the crowd up,” Hammer explained), hope to win over rap fans.» —“M.C. Hammer Nails Down A Royal Reputation” by Lee Hildebrand San Francisco Chronicle Apr. 3, 1988. (source: Double-Tongued Dictionary)