Lizzie Kreider lived on a rural mail delivery route near Lancaster, PA.

https://en.wikipedia.org/wiki/Lancaster,_Pennsylvania

In September of 1906, Lizzie received a postcard from a fellow member of a postcard club.

(The message is signed with a numerical club member number.)

The face of the postcard shows a boating scene on the Charles River in Boston.

A crowd of young people, all wearing white shirts or blouses, have taken to canoes on the River.

(Boating, canoeing, and kayaking are still popular sports on the Charles River.)

https://en.wikipedia.org/wiki/Charles_River

The postcard photograph was published by the New England News Company of Boston and Leipzig.

Beneath the photograph, the sender writes, “Be sure to come to singing on Thursday evening…”

Lizzie’s correspondent has “been looking for you every time.”

The phenomena of the Singing School or of recreational singing groups was widespread since the last quarter of the 19th century.

https://en.wikipedia.org/wiki/Singing_school

(I have found numerous references to “Singings” across Lancaster County.)

Given the absence of music education in schools and the deplorable quality of public singing today, one might hope for a revival of the popular pastime of “the Singing”.