The overture begins with a theme that Warner Brothers cartoon aficionados will recognize, for it was used in their cartoon of 1943 titled 'Inki and The Myna Bird', a cartoon that has not withstood the test of time because of its racial political incorrectness. There is a Myna bird that appears throughout the cartoon and every time it does, this theme accompanies it. It wasn't the first time Warner Brothers, Walt Disney and other animators used parts of classical music pieces for a cartoon. If nothing else, the music was free to use as it was in the public domain.
This first theme was inspired by Mendelssohn's visit to the cave, the sketch he sent to his sister Fanny. It is in B minor and begins in the low pitched instruments of the orchestra and swells up into the higher pitched instruments in imitation of the swells and waves of the sea. The second theme is in a major key and also begins with the low pitched instruments and is more expansive in nature. These two themes comprise the basic elements of the overture. Mendelssohn transforms them and modifies them in various ways as he works towards the coda which develops the opening theme until a climax is reached. The clarinet states the first theme once more in muted dynamics, the flute echoes the clarinet in a short fragment and the work ends.