I can't remember what Auerbach does and doesn't mention in Mimesis, but it seems to me that the first four lines of (the Fairport Convention version of) Matty Groves illustrate his thesis perfectly:
Lord Donald's wife came into the church, the gospel for to hear
And when the meeting it was done, she cast her eyes about
And there she saw little Matty Groves, walking in the crowd.
This scene-setting is so deftly done and in so few words, the listener is almost unaware of the panorama passing before the inner eye, and the amount of information we're being vouchsafed regarding the character of Lady Donald.
Into the same bargain, since we are at the beginning of a narrative, and the word ballad if we have heard it may give us some feelings of unease as to the happy conclusion of the story, the lines are pregnant with the possibilities for disaster and roll out like thunder.
What I do (or think I do) remember from the Auerbach is the unnamed man who makes a cameo appearance (in Genesis) to direct Joseph's brothers in his direction, just as the servant in Matty Groves 'took off his clothes and swam' to make darned sure that tragedy would be served.