This tutorial explains how to map an effect parameter to an audio waveform. You can see an example of this in this demo video.

The basic procedure is to create an envelope from a wave form and paste it onto a specific effect parameter, such as the one that increases the effect level.

You can download the footage used in this tutorial here: dandelion.png and bass.wav.

Step 1
Import both dandelion.png and bass.wav into a new project.  Since the bass.wav track is only 8.9 seconds long, you may want to shorten dandelion.png to match.  Do this by shift-dragging the end of the track, or clicking the i button on the track to bring up the track properties tab and entering a new number for the end time.



Step 2
Drag the bulge maker effect from the effect/video effects/bitmap filters/distortions folder onto the dandelion.png track in the arrangement pane.

Switch the treeview panel (left) to the vars tab. Set the density adjuster effect variable to its highest setting (click at right side of strip, or hover mouse and press the up arrow key.)  This variable is essentially the effect amount for this effect.  Setting it to the maximum value will allow you to see the flower at its loudest.

Now depress the circle drawing tool button on the current tab and draw a circle around the dandelion bud.  This indicates the bulge size/position.  Because you set the density adjuster to maximum, you will be able to view the effect in full in the destination rectangle (top left).

Now you can delete the keyframe you set for the density adjuster (only) so that it doesn't interfere with the keyframes you are going to set in the next steps.  Delete the keyframe by hovering over the strip and pressing the delete key.



Step 3

Go back to the arrangement tab and press the wave button on the bass.wav track.  This brings up the wave display at the top.  Select the entire wave by drawing a box around it with the mouse.  The background will turn a different colour once selected.

Click on the orange button labeled (hover) copy variable envelope. You will see a row of yellow dots appear on the media mixer.  This indicates that the keyframes have been copied to the clipboard.



Step 4
Bring up the density adjuster property tab for the bulge maker effect track.  This can probably be done by clicking the button on the track, as density adjuster was the last variable we manipulated.

Press the paste variable envelope button.  The envelope should appear on the bulge maker track.



Step 5
For this effect to work nicely we want loudest parts of the music to correspond with the maximum value of the density adjuster variable.  The envelope can be adjusted using the orange buttons.  Hover over them to see what they do. 

In this instance the easiest thing to achieve the effect will be to add a value of 40 to all dots.  Do this by typing 40 into the text entry field (on the variable property tab) and then pressing the orange + button (not black, the black ones only affect one keyframe, the orange buttons affect all of the keyframes within the selection).



That's it.  Now you have a singing flower.  Use the export or the preview button on the MediaMixer track to view the results.

Leave comments below if you have problems with this tutorial.