Mickey is the conductor of an orchestra composed of members of the gang for their sponsor Sylvester Macaroni of the Symphony House radio show. Everything goes perfectly in rehearsal, and Macaroni loves the piece and agrees to have it shown in concert.
However, things start to go wrong just before showtime when Goofy accidentally drops the instruments (and himself) down the elevator shaft and the elevator crushes all the instruments. Macaroni and Mickey are unaware of the mishap until the orchestra starts to "play" the damaged instruments. Against all odds, Mickey manages to just barely hold the performance together, despite the ever-increasing lunacy, while Macaroni throws tantrums from inside of his private viewing room. At one point, Donald is so fed up with the chaos caused by the damaged instruments that he packs his things and leaves. Mickey, determined to carry on come what may, points a gun at Donald's head to get him back into playing.
As the piece ends, Macaroni is reduced to tears, believing his reputation to be ruined. But he suddenly lightens up when he hears the thunderous applause from the audience, and he is pleased to find out that they actually loved the bizarre performance.
- Mickey Mouse (voiced by Walt Disney)
- Donald Duck (voiced by Clarence Nash)
- Goofy (voiced by Pinto Colvig)
- Horace Horsecollar
- Clarabelle Cow
- Clara Cluck (voiced by Florence Gill)
- Pete (as Sylvester Macaroni) (voiced by Billy Bletcher)
- Radio Announcer (voiced by John McLeish)
- Donald's Quack Attack, episode #29
- Walt Disney Cartoon Classics: Limited Gold Editions - Mickey
- Walt Disney Mini Classics: Peter and the Wolf
- Disney Favorite Stories: Peter and the Wolf
- Walt Disney Treasures: Mickey Mouse in Living Color, Volume Two
- Symphony Hour would be the last animated short in the Mickey Mouse cartoon series until the end of World War II.
- The music performed in this short is actually the Overture of Franz von Suppé's operetta: Leichte Kavallerie (Light Cavalry). This piece was referenced in the scores of numerous other Disney animated shorts, including The Worm Turns, Cured Duck, and Goofy Gymnastics.
- Though she can be seen among the others playing in rehearsal, Clara Cluck oddly does not appear in the actual performance.
- This film would mark the last theatrical appearance of Clara Cluck.
- Pete's character as Sylvester Macaroni caused a bit of controversy with the Italian community in which they felt that Macaroni was an unfair stereotype on their behalf, considering the fact that he had a thick Italian accent and chain-smoked cigars. This was not the first time that a character (especially Pete) had been attacked due to their portrayal of another character.
- After this animated short, Horace Horsecollar and Clarabelle Cow would not appear in another animated short until Mickey's Christmas Carol.
- The scene (animated by Bernard Wolf) where Donald packs up his things and tries to leave, after which Mickey points a gun at Donald's head to prevent him from doing so, is missing in some versions of the short.
- This marks the final use of the model of Mickey where he had realistic three-dimensional mouse ears.
- The Walt Disney Cartoon Classics: Limited Gold Editions - Mickey VHS uses the original opening and closing titles of this cartoon.
- The 1952 reissue of Mickey's Grand Opera used the music from Symphony Hour during the opening of the short on the Limited Gold Edition Mickey VHS, and the title card for said short was omitted.