'regaining control'

Hi
I have linked some audio to a Warp effect to the single letter of a word. As the audio gets louder and softer the letter deforms. However, at the end I want the letter to be its original state, i.e. no deformation from the effect. How do I set up the expression so that at any given point I can nullify its effect and return everything to normal?

This is the expression on the Warp effect:
thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider")*1.2

This is the expression on the Transform effect:
linear(thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider"), 0, 30, 50, 250)

I can't really cut the audio as it has to continue.

Thanks