Willie Nelson and Waylon Jennings were key figures in the "outlaw country" genre that emerged in the 1970s, a rebellious reaction to the polished Nashville sound dominating country music at the time. Their raw, rock-influenced style and independent spirit helped redefine the musical and cultural landscape of country music. Their collaborative album, "Waylon & Willie" (1978), produced the hit single "Mammas Don't Let Your Babies Grow Up to Be Cowboys", leaving a lasting impact on the genre. Both artists are celebrated for their distinctive voices, Nelson's distinctive guitar playing, and Jennings' distinctive "boom-chicka" rhythm.