To see what I mean, compare SpunkStock. Unless you specifically get the Doom modifier or several stacked Whip modifiers, you can miss several notes in a row without failing. You won't get the coveted SS or even S ratings, but you can still make it through the scene.
Overall I like Beat Banger better than SpunkStock; I particularly love that the beats you trigger are actually thrusts in the sex scene. But the difficulty curve in SpunkStock feels smoother, without the jarring leap from "you suck" to "you're amazing".