You're dealing with heavily oxidized materials here - chemically very different from what was originally present. The shellac will be a hard, insoluble, crosslinked polymer. The tape itself is likely to be brittle, so it breaks apart rather than peeling off.
A commercial paint stripper might soften up the shellac, enough to make removal easier. Scrape with a plastic blade of some sort (putty knife) if you're worried about the finish on the bars.