Recently, I penned my first tags, inspired by one of my favorite musicals (now a film), Into the Woods. I had some friends coming from out of town to see my barbershop concert, and it seemed like a novel way to combine the two.
Giants in the Sky
I also wrote a longer, more ambitious version, meant to capture the different motivations of the ensemble cast (while incorporating a post)...but I realized it was too ambitious for people unfamiliar with the form (and the need to learn several notes and words at once):
Barbershop has a long history of using movies from musicals as an inspiration (for example, this amazing rendition of 76 Trombones from The Music Man). Into the Woods is perhaps too difficult to use as source material given the often simple harmonic content of Sondheim's music, but tags still offer an opportunity to capture the ideas in a snippet and experience the nostalgia of a favorite song.
If you ever get the opportunity to meet some barbershoppers, I highly recommend singing a tag or two!