Fixing duplicate fonts in Fontbook

I downloaded a demo of a music notation program and its screen fonts were messed up. The help forum for the program suggested using Fontbook to remove duplicate fonts. I selected Edit | Select Duplicated Fonts and then Edit | Resolve Duplicates. A number of duplicated fonts showed up. I deleted one of them (perhaps I was not supposed to?) but then none of the others could be deleted. I reopened Fontbook and this time the two Edit | ... Duplicated menu items were grayed out, even though many duplicates still showed up (and couldn't be deleted). After rebooting, this was still the case.

How do I delete the duplicates?

 

(Resolved)

The Advanced Help for the notation software had a link to a Unix program called clearfontcache which did the trick. (It no doubt went through steps that could be done by hand in Terminal.)