Singing — or rather, singing well — is a considerably difficult task. I think that’s pretty much agreed upon, right? But singing, without instrumentals, while harmonizing, on an empty stage in front ...

Few people were aware of the 1994 single “Insomniac” by the rock duo Billy Pilgrim, and it quickly sank into obscurity. But a cappella groups can’t stop singing it. We set out to find an explanation.