The film marked the last theatrical appearance of Horace Horsecollar, Clarabelle Cow, and Clara Cluck for over 40 years, finally reappearing in Mickey's Christmas Carol (1983). Symphony Hour is also the last time that Mickey appeared with either Donald Duck or Goofy in a theatrical film for the same length of time.[3][4][5]
Symphony Hour bears similarities with the 1935 film The Band Concert. Leonard Maltin called this short a "Spike Jones version of The Band Concert".[6]
Mickey conducts a radio orchestra who performs the Franz von Suppé's Light Cavalry Overture. The sponsor (Pete, under the name Sylvester Macaroni) loves the rehearsal and agrees to have it shown in concert. On the night of the performance, everyone is soon ready, except, of course, for Goofy, who accidentally drops all the instruments under an elevator, severely damaging them and thus rendering them unable to make proper musical sounds.
Mickey is left unaware of the unfortunate mishap until the time to go on the air and the musicians start to "play" the damaged instruments. Throughout the outrageous concert, Mickey struggles with anxiety while Macaroni throws a tantrum inside his private viewing room. Macaroni is reduced to tears when the concert ends, believing his reputation to be ruined, but lightens up when he hears the thunderous applause from the audience. He immediately runs to the orchestra room and carries Mickey Mouse in extreme approval, with the latter not knowing anything that happened.
Besides Goofy, other members of the orchestra include Donald Duck, Clara Cluck, Clarabelle Cow and Horace Horsecollar. At one point, Donald is so fed up with the chaos caused by the damaged instruments that he packs his things and leaves. However, Mickey, who is determined to carry on come what may, points a gun at Donald's head to prevent him from leaving. The shot of the gun was cut in some television prints.
