The Sound of Speed To Pitch Effect Calculator (SSTPEC) require a number input of the speed of sound you want it to (eg. 2x speed = 8sec to 4sec = input "2") and output the pitch value you need to set to get that speed. (tolerance:+-5% AND +-0.5sec for the first time)
Maths for the pitch (requires log[2] which Scratch doesn't provide and I found a work around: https://mathsolver.microsoft.com/en/solve-problem/%7B%202%20%20%7D%5E%7B%20x%20%20%7D%20%20%20%3D%20%2010
