Sushi Equalizer

If you want different reactions for different frequencies, you need Trapcode Sound Keys. If you can just fake levels, it's a pretty easy task to take Audio to Keyframes from the Keyframe Assistant and figure out what the range of the audio is going to be by looking at the Graph Editor/Value Graph for Both Channels (the one I usually use) and then set up a linear method using the starting and ending values and the low and maximum scale for each image. Then all you have to do is set the Anchor point at the base of each image.

A sample expression would look something like this:

t = thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider");
tMin = 6; // Minimum slider value
tMax = 19; // Maximum slider value
value1 = 60; // Minimum scale
value2 = 120; // Maximum Scale
y = linear(t, tMin, tMax, value1, value2);
[100, y]

The scale of the layer will be 100, 60 until the audio level reaches 6, then it will grow to 100, 120 when the audio level reaches 19. 

I hope you followed that. 

If you use Sound Keys, you can pick several different frequency ranges and set up minimum and maximum values for different frequency ranges and end up with something that more accurately represents an Audio Equalizer.