Is there a way to automate clean keyframe bounces (in scale) to audio?

Did you try my BeatEdit for After Effects?

Just use the scale pulse preset of its Beat Wiggle.

You can do that without any scripts. Here's the workflow.

• Create a new comp
• Add an audio file to the comp
• Select the Audio layer and use the Animation/Keyframe Assistant/Convert Audio to Keyframes menu
• Select the new Audio Amplitude layer and press "u" to reveal the keyframes
• Both channels slider is almost always the best choice, select that string of keyframes, open the graph editor and make sure that it is set to view the Value graph and not the speed graph by right-clicking in the Graph editor
• Scan the graph and determine where you want the movement to start and where you want the movement to reach its maimum value and make note of the numbers (usually between 0 and about 35)
• Add the layer you want to move and reveal the position property by pressing 'p'
• Alt/Option + Click to start an expression and then type t = and drag the pickwhip to the Both Channels Slider then add a semicolon to the end of the line and press return;
• Complete your expression typing y = and then, using the linear method from the expression language menu in the timeline to generate this line of code: linear(t, tMin, tMax, value1, value2);
• tMin is the minimum value you made note of when you looked at the graph editor, tMax is the maximum value, value 1 is the resting position which should be zero, value2 is the maximum movement in the Y-axis so it could be something like 200
• After you complete the second line of the expression create this array for the last line: [value[0], value[1] - y];

The array takes the current value for X and then subtracts the calculated value of Y from the current value of Y to move the layer up every time the sound passes the threshold. The complete expression would look like this if your audio values were 2 and 35 and you wanted the layer to move up 400 pixels when the sound was the loudest:

t = thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider");
y = linear(t, 2, 35, 0, 400);
[value[0], value[1] - y]

This is what the screenshots would look like:

That will get you there in about 5 minutes. You can also use ease instead of linear in the second line of the expression. 

Entirely depends on what you're after, but most likely you are looking for something like this

http://www.motionscript.com/design-guide/audio-trigger.html

rather than feeding the animation directly from a source. Other options of course could include things like using the smooth() expression functions to even out things or any number of other things. You would have to be more specific about what you actually are trying to do.

Mylenium