It should work.
Are you pickwhipping to a Stopwatch?
Alt Click the Scale Stopwatch for the layer(s) you want to scale with the music, then pickwhip that to the Slider (“E” on the Audio Amplitutde Layer reveals the Left Channel, Right Channel, Both Channels, Twirl Down one of those to expose the Slider, you need to pickwhip to the stopwatch).
This starts at 100% for the layer(s) and adds scales up with the music:
temp = thisComp.layer(“Audio Amplitude”).effect(“Both Channels”)(“Slider”);
value + [temp, temp]*20
The *20 is just to multiply the audio temp values as they are small. Adjust to get the size increase you want.
This just uses the music temp values so the layer is the size of the temp values (again with the *20 so we can see it better).
temp = thisComp.layer(“Audio Amplitude”).effect(“Both Channels”)(“Slider”);
[temp, temp]*20