I have an object set to "Bake Sound to F-Curves" and "LocRot". It's set to move along the z-axis. My problem is that it moves in an upward motion as pictured below. How do I make the object move in a downward motion?
I assume that by "in a downward motion" you mean that you want its jittering effectively reflected over the x axis. There is a way to do this.
Go to the Graph Editor, select the baked-sound f-curve, key N to open the Graph Editor's Properties panel, and open the Modifiers drop down menu (it should be at the bottom of the stack). Add an Envelope modifier and change the settings to this:
You will need to click Add Point before you can change the bottom-most settings (1, 0, and -1.8). This should make the cube move in a downward motion.