I have a Particle System on a grid with an X Velocity of 200 and a Tangent of 60. The Tangent has a keyframe with a sound baked to the f-curve.

The problem is the Tangent get set around 1 instead of 60. I want the sound curve to modify the 60 by a factor around 1.25. That way the Tangent moves between 60 and 75. Also I want more particles to be emitted when the sound is loud.


1 Answer 1


Add an envelope modifier to the baked fcurve to remap to your desired range.

Another way, and one I use extensively in my sound drivers addon, is to bake the sound to a custom property prop, then set up a driver , SCRIPTED EXPRESSION type, with the baked property as a variable (SINGLE_PROPERTY type) var datapath '["prop"]' and make the expression 60 * var.

(var and prop are only suggested names for example case)

To add and bake a property, choose the object you are going to bake on, open the "Custom Properties" Panel, add a property, key in a number, make it a float type (eg 0.0) and then add a keyframe. Select and Bake to Sound from the graph editor as you would any other property.

You can see the datapath on the active fcurve properties panel N used for the datapath of the driver variable, or use the copy data path on mouse menu of the custom property field, and paste into the datapath field of the driver variable.

Go one level further and add another custom property and use it in the driver as the multiplier, then you can change the amplitude of the baked fcurve effect directly from a slider in the UI.

To make it easier I have put together an addon, Sound Drivers.

This post is also relevant to What's the range of values on a sound-baked f-curve? .

  • $\begingroup$ How do I bake the sound to a custom property? Is that something I need to do in the text editor? Because I don't have much experience with the text editor (not that I'm hesitant to try, though). $\endgroup$
    – Caleb Salyards
    Oct 24, 2015 at 22:57
  • $\begingroup$ Edited answer with details of how to bake custom prop. $\endgroup$
    – batFINGER
    Oct 25, 2015 at 6:26
  • $\begingroup$ So, I don't know what's wrong, but I followed your instructions and the prop variable seems to change correctly, but it just won't link to var. Here is a picture of the graph editor. See anything wrong? $\endgroup$
    – Caleb Salyards
    Oct 25, 2015 at 23:20
  • $\begingroup$ Aww yea! Now we're talkin! Thanks so much for your help. $\endgroup$
    – Caleb Salyards
    Oct 26, 2015 at 20:27

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