Sound FFT Modifier
Updated: 7 Aug 2025
Generate's trigger values form a certain region of a sound's frequency spectrum.
Sound FFT Modifier
Method #
An audio-reactive modifier that can be precisely tuned to be triggered between specific values of frequency and amplitude. This modifier is really useful for picking out very specific elements of a sound to drive audio reactive elements of a scene. For example, creating a value that is triggered ever time a kick drum is hit, which can then be used to drive an effect.
In order to use this node, a Sound Loader node that has an audio file must be present on your nodegraph.
This node uses it’s own overlay on the Notch builder viewport, that displays the spectrum of the audio, and allows you to draw a rectangular region over the spectrum. To open this overlay, go to the node’s properties, and click on “Overlay” or “Mini Overlay” next to the property “Preview in Viewport”.
This will open a new overlay in your viewport. This shows the amplitude of each frequency within the audio, this is the result of the Fast Fourier Transform. The overlay graph will show frequency on the X axis, and amplitude on the Y axis.
Click and drag on this graph to create on this overlay graphic to draw the bounds of a rectangle.
When there is an audio signal in the frequency and amplitude range specified by this rectangle, the output of the modifier will ramp from 0 to 1. When audio stops being present in that region, the output value will ramp back down to 0. The time and shape of the attack and decay sections of this envelope can be adjusted withing the nodes properties.
A good way to work with this is to let your audio play, and watch the spectrum on the overlay. Work out which bit of the spectrum corresponds to the sound you are trying to pick out, and then draw a rectangle over that region.
This node has been designed to let you extract multiple triggers from one piece of audio n the most efficient manner possible. Rather than creating multiple Sound FFT Modifier nodes, you can add multiple regions to one Sound FFT Modifier. This is done with the “Add Region” button in the property window, or by adding a Sound FFT Region modifier and parenting it to the Sound FFT Modifier.
Working in this way ensures that the FFT calculation needed in this node is only performed once, so it is more computationally efficient than using multiple Sound FFT Modifiers and calculating the FFT multiple times.
Selecting an FFT Region Modifier will let you draw a new region on the overlay of your original FFT overlay.
Parameters
Parameter Details Rect X0 The normalised lower frequency value of the trigger region.
Rect X1 The normalised upper frequency value of the trigger region.
Rect Y0 The normalised lower amplitude value of the trigger region.
Rect Y1 The normalised upper amplitude value of the trigger region.
These properties control the core behaviours of the node.
Parameter Details Current Value Shows the current value of the effect. Cannot be directly changed.
Blend Amount The amount to blend the input modifier’s value with it’s new value.
Sound Sound file used for the modifier.
Looping Controls whether the sound loops across timeline loops or resets. Only functions if a sound is selected within this node and a sound source isn’t connected to the Sound input.
Operation TBC
- Add : Adds to the parameter value.
- Subtract : Subtracts from the parameter value.
- Multiply : Multiplies the parameter value.
- Replace : Replaces the parameter value.
Scale Scale the modifier’s output value.
Offset Offsets the modifier’s output value.
Channel Determines which channel of the incoming audio the modifier will react to.
- Stereo : The modifier will react to both the left and right channels.
- Left : The modifier will react to the left channel only.
- Right : The modifier will react to the right channel only.
- Mid : The modifier will react to the sum of the left and right channel divided by two.
- Side : The modifier will react to the left channel minus the right channel divided by two. This gives you the parts of your incoming audio that have been panned to one side.
Time Offset Move the audio coming into the FFt forward or backward in time.
Attack The attack time of the trigger envelope in seconds.
Decay The decay time of the trigger envelope in seconds.
Attack Shape Power Controls the curve of the attack section of the envelope.
Decay Shape Power Controls the decay of the attack section of the envelope.
Preview In Viewport Opens the overlay. Definitely use this.
Modifier Values Read only graph to show the output of the modifier.
Inputs
| Parameter | Details |
|---|---|
| Rect X0 | The normalised lower frequency value of the trigger region. |
| Rect X1 | The normalised upper frequency value of the trigger region. |
| Rect Y0 | The normalised lower amplitude value of the trigger region. |
| Rect Y1 | The normalised upper amplitude value of the trigger region. |
These properties control the core behaviours of the node.
| Parameter | Details |
|---|---|
| Current Value | Shows the current value of the effect. Cannot be directly changed. |
| Blend Amount | The amount to blend the input modifier’s value with it’s new value. |
| Sound | Sound file used for the modifier. |
| Looping | Controls whether the sound loops across timeline loops or resets. Only functions if a sound is selected within this node and a sound source isn’t connected to the Sound input. |
| Operation | TBC
|
| Scale | Scale the modifier’s output value. |
| Offset | Offsets the modifier’s output value. |
| Channel | Determines which channel of the incoming audio the modifier will react to.
|
| Time Offset | Move the audio coming into the FFt forward or backward in time. |
| Attack | The attack time of the trigger envelope in seconds. |
| Decay | The decay time of the trigger envelope in seconds. |
| Attack Shape Power | Controls the curve of the attack section of the envelope. |
| Decay Shape Power | Controls the decay of the attack section of the envelope. |
| Preview In Viewport | Opens the overlay. Definitely use this. |
| Modifier Values | Read only graph to show the output of the modifier. |
| Name | Description | Typical Input |
|---|---|---|
| Sound | TBC | TBC |
| Blend Amount | TBC | TBC |
| Scale | TBC | TBC |
| Offset | TBC | TBC |
| Attack | TBC | TBC |
| Decay | TBC | TBC |
| Attack Shape Power | TBC | TBC |
| Attack Shape Power | TBC | TBC |
| Rect X0 | TBC | TBC |
| Rect X1 | TBC | TBC |
| Rect Y0 | TBC | TBC |
| Rect Y1 | TBC | TBC |
| Time Offset | TBC | TBC |