Key frames on audio beats

In addition to the info above, if your music track has a really defined kick drum or some other element that you can isolate with equalisation, you can use that as an animation tool.

Nest your audio in a precomp and apply the Paramaetric EQ effect.  Adjust to isolate the frequency of whatever you want to use as an animation trigger - the kick drum, for example.

Then follow the instructions provided above to generate keyframes from audio, but use the precomp'd layer as your audio source.  You can do this multiple times with different frequency ranges, so you can have different things animate based on frequency.  For example, you could animate a character who's legs bend on every kick drum (low frequency) and whose arms raise every time there's a cymbal crash (high frequency).

Take a look at this tutorial that I created. It should cover everything you need.

You can convert audio volume into keyframes and then use the property link to connect a layer property like scale to it.

1 - Add the audio file to the timeline & select the layer

2 - Choose Animation > Keyframe Assistant > Convert Audio to Keyframe. This gives you a new layer, probaly named [Audio Amplitude].

3 - Open the new layer's properties by tapping "U" on the keyboard.

4 - In the Timeline open the property you want to link.

5 - Use the pick whip (that the spiral in the Parent & Link column). Drag it to the slider property you want to link to. I usually use the Both Channels slider. 

It writes an expression, you'll probably need to add a multiplier to the expression since the slider values are so low. I usually multiply it by 10 or 20 by adding "*10" at the end of the expression line.

https://youtu.be/9uIiQnGhhGU

You can create markers by hitting the multiply * sign on the numpad section of your keyboard while a RAM preview plays. Oldest trick in the book with the only real limitation being that you can't have an infinite number of markers...

Mylenium