How to create a resulting wavetable from a wave source set to a pulse wave, to morph into an audio source after the middle of the lenght, without the audio source influencing the beggining of the wavetable?

The title says it all. When i import an audio source into a wavetable made out of a single wave (eg pulsewave ) even though i put the keyframe in the middle of the timespan, it automatically influences the beggining/first half being this first half the pulse wave. How can i make them only turn to one another in the middle lengh??? without affecting each other before and after?

audio_kfstfu.vital (209.6 KB)
With audio keyframes, we don’t get a whole lot of flexibility. To get the effect you want, I used a wave filter modifier, set to square mode and left position to max, to null out all the audio file before the keyframe switch in the middle. Immediately after the middle, the desired location of switching, I made another filter keyframe that let everything in the audio file through. The preset file provided should do a better job explaining than I did.