In order to get objects to react to audio you need to use the Parameter Behavior called Audio. A short cut, for example, If you want the scale to animate right click on Scale in the Properties section and choose Audio. If you look at the Audio Behavior in the Behaviors tab you will see the "Apply To" section is linked to the Scale. Hope this helps and best of luck.
Sorry......I'm new to Motion and I will need a little more information. I have the clip loaded form FCP with a color matte to get it in there but Motion says "nothing selected" but the audio does
play. Now what?
OK, I'm 3000 miles away from my Motion setup at the moment so can't actually test this out for you myself, but off the top of my head, try this:
Use the freehand shape tool to draw a horizontal line across the screen. Don't try and make it perfectly straight, it helps to have a "hand-drawn without a ruler" sort of feel. Then apply Behaviours>Shape>Wriggle Shape. Play around with the settings and you'll see that this behaviour will animate the positions of the points that make up the line you've drawn, which will hopefully give it a sort of waveform look.
To make your audio track drive the animation, apply the Audio parameter behaviour to the amplitude parameter of the Wriggle Shape behaviour. You will probably want to add some randomisation as well, and try and find a way of limiting the movement of the points to the vertical plane only.
As I say, if I wasn't 3000 miles away from my Motion setup I'd be able to offer more detailed suggestions, but hopefully you might find the above to be a useful starting point.