Shape note singing is one of America's oldest musical traditions, and it is having a bit of a revival now because of an updated songbook. (SOUNDBITE OF MUSIC) SIMON: Laura Atkinson and Justin Hicks, ...

DULUTH — Once a month, typically on a Sunday afternoon, the Friends Meeting House is filled with voices singing together. It's not a performance because everyone present is involved in the singing.

An old religiously inspired songbook that uses shape notes for people who can't read music got a major update and is attracting younger singers. Hundreds of singers from all over the world gathered ...