Zork Nemisis-stuck in crystal cave,need help

After figuring ou the whacky orchestra at the conservatory theater and going backstage, you wind up in a cave where you have to figure out a sequence of notes and which blue crystals they belong to. I have thrown the green crystal and the wafer into the boiling pot and gotten the clear crystal, have figured out the location of the 4 notes(blue crystals) from the map, but cant get anything to happen-supposed to pick up a copper symbol(not sure where) after the correct notes have been played.Would sure appreciate some suggestions- have looked a 2 or 3 WTs, but they all say the same thing.

You are supposed to hit the four notes, and then click on the crystal inside the bath to get the fifth note. It should shatter and then give you the copper symbol.