To be fair, we have know idea who originally penned this poem, so it might be more than a little difficult—okay, impossible¬—to pin down a calling card for this poem's style and features. But we've got a ballad in Scottish dialect, which we can tell right off the bat, so that's enough to be getting on with Shmoop thinks.
Plus there's that whole question-and-answer format that this "Lord Randall" has got going on. This particular format does a lot more than give us a formal template for the poem. It also adds to the feeling of suspense and the building sense of melancholy that distinguishes "Lord Randall" from the rest of the ballads you might encounter on your travels along the Scottish moors.
Though this story could easily be told in a more straightforward way by a third person narrator, or by a single, first-person narrator, we gain a lot through the give-and-take of the dialogue form. We readers (or listeners) are in the position of Lord Randall's mother; we want to know what happened to him, and his cryptic, gradual answers only makes us feel more and more of her mounting concern.