The auditorium and stage of the Paris Opera House seen here was the same set built for the 1925 version. It still stands at Universal Studios today, and has been used for countless other productions, including Thoroughly Modern Millie (1967) and The Sting (1973). It is the oldest remaining film set in the world.
The original script revealed Claudin to be Christine's father, who abandoned her and her mother in order to pursue a musical career. When this was excised from the final film, it left Claudin's obsession with Christine unexplained.
On 21 May 1943, the finished film was rejected by the Hays Office because of a "number of unacceptable breast shots of Christine" in her dressing room. It has not been determined if the offending scenes were deleted or re-shot, but the film was released in Aug 1943 with Production Code Administration approval.
In the scene where the three heroes escape the Phantom's crumbling lair (which involve the three characters running from a cave in) only Susanna Foster actually appeared in the scene, the two male stars were deemed too important to film such a risky scene and had stunt doubles.
The Universal Studios' stage 28 floor-foot print, built for the 1925 B&W Lon Chaney "Phantom of the Opera" feature film, is enormous. The European horseshoe Paris Opera Theatre's three tiered box audience seating area surrounds the floor audience ramped area. The master wide-shot from the top rear box seat area encompasses the stage proscenium, orchestra pit, and the chandelier. The top of the interior theatre ceiling master shot is completed with a matte painting. The audience area is one third of the stage's foot print. The North end of stage 28 encompasses the raised stage area. What really makes this stage unique is that in 1925, an elaborate 30'-0" diameter mechanical turntable sits in the center of the front stage area, allowing forty (40) feet from the back edge of the turntable to the rear stage back-wall. The basement of stage 28 houses the original turntable mechanical mechanism to turn the 30' diameter turntable. All of the mechanics for the turntable have remained intact, sitting in their original structural position. The turntable centers on a center cylindrical shaft, with triangular inverted bracing branches, welded to the center shaft, similar to an inverted umbrella brace. The entire weight of the turntable is thrust upon this center turning spindle. After the original film was completed, the turntable area of the stage floor was covered with three layers of 3/4" thick plywood 4'-0" x 10'-0" sheets, which allowed future film sets to be built upon the turntable stage area for feature filming. When a camera crane is used on the stage, allowances have to be considered with the turntable's floor position, related to the film set requirements. The original stage had a theatre pin rail system with hanging pipe arbors for electrical lights, existing on the stage right area. The raised stage area was utilized for feature film "process photography" because of the depth required for a film projector onto a rear screen, enough room for a camera and crew, with an acting/performance area in front of the screen. The projector camera has to be in direct center of the filming camera's lens point of view position, with a depth of field allowance. The 1943 Universal Studios Technicolor remake of "Phantom of the Opera" stripped the plywood floor covering in order to utilize the turntable for the film's stage production numbers. The turntable mechanism was tuned up and used. After this 1943 film was completed, the stage flooring was installed covering the turntable. The turntable has never been used since the 1943 feature film. The interior Opera House theatre has been filmed, and the production stage area of stage 28 has been host to many feature and television films.
Because the war in Europe made it so difficult to track down who had the rights to most operas (coupled with the studio's reluctance to pay the required royalties), all the operas performed in the film were either in the public domain (i.e., copyrights had expired and anyone could use them without paying royalties)) or were based on classical music that was in the public domain. The filmmakers were able to slip in a reference to the opera "Faust" (which featured heavily in the original novel) by having Christine appear in the Marguerite costume as she comes off stage at the end of the film.
Despite his fearsome reputation Susanna Foster remembered 'Jack Pierce' as being a sweet caring man that took the time to teach her how to apply her makeup to best suit her features, despite the fact that he was not assigned to work with her. Any time that he saw her where she was not made up as he had suggested he would pretend to be mad and tell her off, saying "You are not doing what I said".
Of the three "operas" in the film, only the first, "Marta," by Friedrich von Flotow, is an actual opera. The second, "Amore et Gloire," is adapted from music originally written for piano by Frédéric Chopin: the overture and opening chorus is taken from the "Military" Polonaise in A major, Op. 40, No. 1; the duet between Anatole and Biancarolli is taken from the Waltz in C-sharp minor, Op. 64, No. 2; and the music for Christine's aria/duet with Anatole is taken from the Nocturne in E-flat major, Op. 9, No. 2. The music of the third opera, "Le Prince Masque de Caucasie," is actually excerpts from the finale of Pyotr Ilyich Tchaikovsky's "Fourth Symphony".
Nelson Eddy's hair was to be dyed black because of script requirements for his role of operatic baritone Anatole, maybe intending to refer to Norman Kerry looks in the silent version. According to the documentary included in the 1943 version DVD, Nelson only agreed when Jack Pierce, Universal make-up master, developed a one-day tinting that could be washed out after each day's shooting, allowing Nelson (who was of Dutch ancestry) to recover his characteristic blond hair.
Susanna Foster, the then 19-year-old soprano in the leading role, was asked by Nelson to join him for a concert tour, but she declined feeling she was too young (from "Nelson Eddy, America's favorite baritone" by Gail Lulay).
Nelson Eddy's voice was recorded this time by Universal sound technicians, who claimed to have developed a better system that the one used by MGM. There is an anecdote of Nelson being at first annoyed as he didn't recognize his own voice and thought they had used someone else, until the sound team convinced him that it was really him with an improved sonority (from "Nelson Eddy, America's favorite baritone" by Gail Lulay).
Claude Rains accepted to play the Phantom under the condition that no overdone disfiguration would be made. Jack Pierce succeeded in fulfilling his requirement, according to the documentary included in the DVD release.
Universal Studios' Stage 28, originally built for the 1925 feature B&W film "Phantom of the Opera," was used, again, for the 1943 Universal Studios feature Technicolor film "Phantom of the Opera" starring Nelson Eddy, Susanna Foster and Claude Rains. The interior Paris Opera theatre has been used for the 1966 Alfred Hitchcock feature "Torn Curtain," the Ross Hunter 1967 feature film musical "Thoroughly Modern Millie," and the Universal CBS TV series "Murder, She Wrote.