In 1943, behind the barbed wire and armed checkpoints of Oak Ridge, Tennessee, a country gospel harmony group sang for the scientists secretly building the atomic bomb. That Manhattan Project gig gave the Oak Ridge Boys their name — and launched an 80-plus-year saga that runs from sacred quartet music to multi-platinum 1980s country-pop arena stardom.

Their story is a masterclass in survival and radical reinvention: desperate years singing backup on anything that paid, a sound that fused gospel arrangements with pop sensibilities and country instrumentation, and finally the 1981 phenomenon Elvira, which made four-part harmony a pop culture institution. It raises a question — when a band outlives its members' eras, does it become immortal?

• Got their name performing for Manhattan Project workers inside the secret Oak Rid ...