1939
I suspect that right about now there are many church choirs out there that are right up to their floppy bows in performances that involve extended lines of "Gloria" and "Halleluja," and "O Holy." In some cases their beautifully starched and pressed cottas represent the labor of the Ladies' Auxiliary. With luck, the ladies would have been able to plan ahead and weren't slipping away from the Thanksgiving table to sew a just a few more hems to get the choir ready for the service for the first Sunday in Advent.
The boys in this choir from the 1930s look as though they're on the verge of making a run for the ice-cream truck (or just disintegrating into a scrum.) Wouldn't you love to know what the photographer had just said?
Note the little gussets under the arms - a relic of the ancestors of this garment.