CotD: Disney claimed “Melody (Adventures In Music)” was the first 3D animated cartoon; it was just Disney’s first animated 3D film ~ http://www.bcdb.com/cartoon/6321-Melody_%28Adventures_In_Music%29.html
Melody (Adventures In Music) (1933) — Disney Theatrical Cartoon
Professor Owl teaches his music class (full of birds) about melody and its importance to the world of music. It’s all around in nature. Only birds and man can sing; man “sings” even when he speaks. We see a quick survey of the stages of life, as captured by songs: the Alphabet Song for primary school, “Here Comes the Bride,” “The Old Gray Mare,” etc.
Some inspirations for song are outlined in song (such as love, sailing, trains, the West and motherhood), but “we never sing about brains.” Finally, an example is shown of how a simple melody can be expanded into a symphony: an elaborate version of the simple tune which opened the lesson.