The plan was to trap von Glover, force him into wolf form with the opera&chandeliers and then make the detective shoot him. Because the building had wrong dimensions, the opera didn't have the expected effect - though von Glover DID feel himself uncomfortable (tried to leave his seat), but he could remain in control. It wasn't the opera but the sight of the werewolf Gabriel - and the sound of his howling - which pushed him beyond the edge and made him transform.
...and after that, there were still other complications in the plan, but you already know that! :)

The crystals would, if placed correctly in the original Wittelsbacher Theater, in the proper pieces of music create a humming or particular hertz of waves that would force Von Glower into his animal form.

According to the diary entries, Ludwig almost had "the horror", ie the change to animal form, come over him during a rehearsal of the almost completed opera before Wagners death. With Wagner he then concocted a plan to create a larger reaction with the crystals, according to the diary entries, Wagners letter and the diary of Wagners wife.

This would probably also have worked, if it hadn't been for the history grad-student Grace forgetting the fact that the original Wittelsbacher Theater was bombed during the 2nd World War, so that the crystals weren't placed properly according to the original diagram.

As Bolch said, Von Glower felt the vibrations with the music, but it wasn't enough to push a 200-yearold werewolf over the edge, but as the Lychantropy book also explained, Gabriels howling along with the music did push him enough over the edge to transform as soon as he was out of sight from the opera crowds.

Basically they did end up having a hell of a lot of luck, Gabriel escaping and all, but what's a Gabriel Knight mystery without a bit of luck? ;)

So if the only purpose of the crystals was to effect the transformation, what use would Wagner and King Ludwig have of them? Ludwig was particularly anxious to hide his condition from his subjects. I thought the purpose of the invention was to cure lycantrophy, not to expose the King as a terrible monster.

I think they wanted to use the opera for the exact same purpose as Gabrieil and Grace: to expose von Glower and than make the audiance kill him.

Thanks for the answers; I think I get it now.

So if I'm understanding it right, the opera could be performed anywhere and a werewolf in the middle of it would be forced into his wolf form. (This is what happened to Gabriel, but only because he sneaked onto the stage.) The precise dimensions of the Wagner theater and the locations of the crystals were meant to direct and focus that energy onto a specific location within the audience. (Where Von Glower was seated.)

But since the dimensions were wrong, if Gabriel hadn't been there and been forced into his wolf form, Von Glower never would have been forced into his wolf form either.

Hmm. I understood it a little differently:
Since the Wagner theatre has the wrong dimensions, the crystals' effect is lessened. But since Gabriel was bitten just a short time ago, the effect is still strong enough to force him into the wolf-form. Von Glower, as being a very old and experienced being, can resist those vibrations better. But in combination with Gabriel's howls the crystals are strong enough to make him transform.
So, as far as I understand it (of course I can be wrong), the opera alone performed at a random place would not be enough.
If Gabriel would have stayed in the room he was locked into, he would probably not have been affected, because he would have been too far away from the vibrations of the crystals. But then Von Glower would not have transformed into his wolf-form either.

I understood it the same way you did, ClusterRat, I think the location was a vital part of the plan, hence the difficulties with making it work in the now altered location.
IIRC there was also a note by Ludwig somewhere stating that he was willing to accept the fact that if this plan worked it would mean he would most likely be killed as well... I think that the point was that in helping to defeat the werewolf his soul would still be freed.

WildHobgoblin... Wasn't there somewhere said, that the person's soul could still be saved, as long as the "wolf" has never killed a person? Probably THAT was the wish of Ludwig. To be stopped before he actually gave over to the wolf-nature and killed people? If you beliefe in it, having your soul saved might be worth a lot more than living on like... forever as an evil being.
I think you are right. Ludwig might have been killed during that "original" performance of the opera. But his soul would, at least in that he believed, be freed.

It's been a while since I've played the game (or read the book), but I believe Ludwig's original intention was to force Von Glower into wolf form and have some one there ready to kill him (maybe it needed to be Ludwig himself. I don't recall the specifics). By killing Von Glower, Ludwig's curse would be broken (as Von Glower was the alpha wolf), just like Gabriel's was at the end of the game - by killing him.

KyoshoBallard is right. The book that Grace finds in the Schloss Ritter library states that:
"A person who becomes a werewolf against his will . . . is not completely damned until he tastes of human blood. Once he does, his soul is eternally damned and nothing may redeem him. Even without tasting of human blood, however, as long as the taint [of cursed werewolf blood] lays on the immortal soul, it cannot enter into Heaven, and will remain chained to the mortal plane upon death."

Therefore, Ludwig's soul would only be free to go to heaven if the Black Wolf (his alpha) if Ludwig caused the Black Wolf's death. Because Ludwig died while Vonn Glower did not, Ludwig's tainted soul remained on earth to haunt/guide Grace.

What I want to know is whether Ludwig, in constructing his plan with Wagner, and in guiding Grace to Wagner's opera, played enough of a role in Von Glower's death to retroactively liberate his soul or if he's out of luck since he died while the werewolf blood curse was still upon his soul.

Oh, I understand, and I think we're in agreement there... I just recall that somewhere Ludwig mentioned he would likely die as well, but his soul would be free, since he was a religious man that must have given him some hope. Of course, if the music would have been strong enough to change von Glower, Ludwig would have changed as well, and in the unrest that would have followed would probably have been killed along with his alpha.

Alright, so I started to rummage around in the novel (since it's a bit easier to navigate than the game ;) ) and while I didn't find the passage I thought I remembered (Ludwig accepting he might die during opera) I found a part that seems to confirm that Ludwig would indeed be freed if the opera-plan works out.

Here it is (no copyright infringement intended, just remove if it's not okay to have this here):

Edit: Found one small reference, ending of ch 4, in the journal of Cosima Wagner (Ludwig acknoledging possible death as an outcome).

Thanks for clearing up that point. As far as I can tell, the game leaves the question unanswered, so it's good to have a canonical source to provide resolution. :-)