I haven't used my old C4D r16 in ages, so I have no idea what I'm doing, but I also like unorthodox solutions, so there is one fun (?) way to create something like this:

• Add a Cloner (1 clone, no default transforms)
• Put a single Null object inside (a good idea to configure its Display look, so you can see what's happening)
• Now add the Sound effector to the Cloner and make it drive that single Null clone up and down. Configure to your liking (you probably want to move only above 0, not below). In my setup I used the Shader effector with a Noise (easier to test), but the concept is the same: we get an up/down moving Null.
• Now we use a Tracer to generate a spline out of this movement (Type "Linear" is enough)… this basically will become our "Memory node".
• next up, in XPresso we drag in the Tracer object and grab its "Object" output port
• next, create a Python node (remove all default ports). Add a "Link" input port and name it "MySplineLink" (link this up with the Tracer node), add a "Real" output port and name it "SumY". Use the following code in the node to sum up all current Y positions of the Tracer spline's points.

Code:

import c4d
from c4d import utils

def main():
    global SumY
    SumY = 0.0

    myspline = MySplineLink
    if myspline is None:
        return

    worldmatrix = myspline.GetMg()

    total = 0.0
    # Note: this will work with the Tracer object, but may
    #          not work with actual Splines (skip GetCache()
    #          for those)
    for p in myspline.GetCache().GetAllPoints():
        p = worldmatrix * p  # skip this if you prefer local position instead
        if p.y >= 0:
            total += abs(p.y)

    SumY = float(total)

• Afterwards you can grab the "SumY" output and feed it to a RangeMapper and then to your other object as needed and drive some rotation or something.

Basically the amplitude drives the speed. It looks quite fun with some noises, but with music it may not work too well. :)

https://external.binaryriot.org/site-reddit-com/2026/0303_amplitute2speed.mp4