You know this piece, just not the full form. Skip to 2:20 if its still a mystery. :)
Although in his lifetime Ponchielli was very popular and influential, in introducing an enlarged orchestra and more complex orchestration, the only one of his operas regularly performed today is La Gioconda. It contains the great tenor romanza “Cielo e mar”, a superb duet for tenor and baritone “Enzo Grimaldo”, the soprano set-piece “Suicidio!”, and the ballet music “The Dance of the Hours”, known even to the non-musical from its use in Walt Disney’s Fantasia in 1940, Allan Sherman’s novelty song, “Hello Muddah, Hello Fadduh”, and other popular works.