help me with maths - shaping a signal (audio domain)

I wonder if there is an better way to achieve what I have in the attached patch. I want to shape a signal in the range between 0 and 1 so that it grows slowly for small values and faster for big ones. Sort of an inverse stauration maybe. Results should aways stay between 0 and 1. (In my case small negative value in the multiplication, eg. 0.6 produces ranges from aprox 0.5 to 1.)

Thanks, Joerg