Malady, Medley & Melody

Malady is an illness of an animal: “The cattle died of an incurable malady and his business ran into ruins.”
Medley is a piece of music made up of a series of short tunes: “The actor performed on the medley of songs of the best of his movies in the award ceremony.”
Melody is a pleasant and pleasing arrangement of sounds: “The pianist played a mellifluous melody and won several accolades from the audience.”