At the peak of their fame — Grammy Awards, a chart-topping TV theme song, two decades of defining bluegrass — Lester Flatt and Earl Scruggs walked away from each other. The greatest duo in bluegrass and country music history wasn't broken by scandal or money, but by the cultural revolution of the 1960s and the songs of Bob Dylan.

Scruggs, the relentless innovator, wanted to chase the young crossover audience with Dylan covers and modern sounds. Flatt, the traditional anchor, believed their duty was to preserve the heritage they helped create — and in 1969 that friction shattered a 20-year partnership. Their story asks whether great creative teams actually need the tension that eventually tears them apart.

• Flatt and Scruggs hit number one with a beloved television theme song and won Grammy Awards

• Dobro player Un ...