From another straight shaver... Interesting.
Indeed - this is one of the most challenging parts in grinding a razor. Most important here is grinding the hollow to a maximum point. But you must keep in mind the following steps, means what we call "Pliesten" -rough polishing with wheels glued with emery and final polishing. Especially the rough polishing takes away material. So the sound after grinding is not the final sound. And if you go one step too far - its over. Means the razor than becomes a somehow tinny sound. Solingen razor grinders call this "klatschen" - clapping.To find the right thickness of the hollow during grinding takes you years in experience.
Second the the form and thickness of the belly is an important criteria for the sound. If the belly isn't rounded well to a thin, perfect convex form all the way down to the edge, the sound isn't clear.
Werner Breidenbach is absolutely perfect in making singing razors. At his time for Paul Drees he worked mostly for the italien market. And the whoelsalers in Italy often put a tuning fork to their orders. The fork was tuned in "f" and all razors had to sound in this tone....
Only a very small number of razor grinders had been able to make those razors, number for number in thousands of pieces.
Stay sharp
Peter