I got this autograph-book where the previous owner have used tape above some of the autograph - and when I try to remove it I find the signature attatched the back of the tape:
I would leave it alone. The tape does not detract from the autograph very much. It is similar to a check that may have a stamp touching part of the signature.
The only thing I can think of is to put the page in a freezer as this will make the glue of the tape brittle and it will come off easier. But please try it on a less valueable piece first and also the glue will probably stay on the paper. It is try and error on this one.