The innovations of Run-D.M.C., LL Cool J, and new school producers such as Larry Smith, and Rick Rubin of Def Jam Recordings, were quickly advanced on by the Beastie Boys, Marley Marl and his Juice Crew MCs, Boogie Down Productions, Public Enemy, and Eric B. & Rakim. Hip hop production became denser, rhymes and beats faster, as the drum machine was augmented with the sampler technology. Rakim took lyrics about the art of rapping to new heights, while KRS-One and Chuck D pushed "message rap" towards black activism. Native Tongues artists' inclusive, sample-crowded music accompanied their positivity, Afrocentricity and playful energy.