Barbershop arranging benefits from a very clear-cut sense of method. There are well-defined procedures you go through that, operated with a modicum of intelligence and musicianship, will result in competent arrangements.
However, they only really work well on the kind of songs that barbershoppers traditionally sing: those with well-defined melodies and varied, functional harmonies – songs whose original form was written down. Songs whose original form was in recorded form – i.e. most pop music since the 1960s - don’t respond nearly so well to the barbershop method. But barbershoppers still want to sing them, so we have to figure out ways to make this work for them.
There are two sides to this: first, how to arrange in a way that works for the song, and second, making sure this still fits the expectations and performance habits of the singers.
Some of the issues we encounter include: