"Buddy, better get on down the line" (I learned it from a Kingston Trio album .)In it, a woman tells her wandering beau to look out, here comes the train, and she's leaving. It's a good song for an alto with punch.

Or for something more gentle, how about "In the Pines?" I especially love the last bit:

Oh, don't you hear them mourning doves,
that fly from pine to pine?
Mourning for their own true love,
just like I mourn for mine.