Category: motion graphics

Animating with audio

Getting audio key frames out of After Effects using Trapcode Sound Keys

You can use Trapcode Sound Keys to create audio driven animation in After Effects. You can also save the key frames to a text file, and use them in other animation applications.


1. Create a solid layer.
2. Apply the Sound Keys Effect to the solid.
3. Add an audio layer to the timeline, then assign that layer to drive Sound Keys from the “Audio Layer” drop-down.

4. Select the frequency range that you want to capture from the spectrum.
5. Adjust the work area in the time line to reflect the range of keys that you would like to capture.
6. Click the “Apply Button”. Sound Keys will create keys in the timeline.

7. Select and copy the keys. Paste the keys to a text file.

Should look something like this:

Adobe After Effects 8.0 Keyframe Data Units Per Second 29.97 Source Width 900 Source Height 506 Source Pixel Aspect Ratio 1 Comp Pixel Aspect Ratio 1 Effects Sound Keys #1 Output 1 #22 Frame 0 0 1 0 2 0 3 0 4 0.000261479 5 0.00608461 6 0.0153011 7 0.0274689 8 0.0395869 9 0.0493024 10 0.0562797 11 0.0557284

Extra information about copying and pasting data.

Slider Control in After Effects

You can link the Slider Control expression control to properties in After Effects to create a gui slider interface with a key-able value. An easy way to do this is to do the following.

  1. Make a null layer. Apply the Slider Control expression control effect to the null layer.
  2. Create an expression by option/alt clicking on the “stopwatch” of the property.
  3. Use the pick whip to connect the property to the Slider Control.

You can also link individual values of properties, the x position for example, to the slider if you highlight that value and then connect via the pick whip. You must be able to access the individual arrayed values of the property, so write your expression as below, for example:


Highlight the value “position[1]” then use the pick whip to connect to the Slide Control. You will get this new expression as a result (if your null is named controllerNull):

[position[0],thisComp.layer("controllerNull"). effect("Slider Control")("Slider")]

Download example scene

The following expression is used to link a series layers to the slider. The “index” value is used to echo the layer number, here the z position of a 3d layer. The slider control is used as a multiplier on that value. The result is an accordion like effect.

[position[0],position[1], index*thisComp.layer("controllerNull").effect("Slider Control")("Slider")]

After Effects tips

Command + forward slash (apple), or control + forward slash will bring selected footage items into an open composition.

Command + option + forward slash (apple), or control + alt + forward slash will replace selected footage in the timeline with selected footage from the project panel.

Hit the asterisk key on the numeric keypad to add a layer marker to a selected layer at the current point in time.

Command/control + Y creates a new solid. Command/control + shift + Y opens solid settings.

Press the u key to reveal all key frames. Press uu to reveal all modified parameters.

To match the work area to a layer’s duration: select the layer, then type “ibon“. i sends the time indicator to the in point of the layer, b sends the in point of the work area to match the time indicator. o sends the time indicator to the outpoint of the layer, n sends the out point of the work area to the outpoint of the time indicator. Better yet use command+option+b to match the work area to the duration of all selected layers.

Use the bracket [] keys to move layers in/out to the time indicator. Option+bracket will crop the in/out points to the time indicator.

To go to the first or last frame of the work area, press Shift+Home or Shift+End.

Show only properties with keyframes or expressions: Press U

After Effects Keyboard Shortcuts