This question is based on General Literature Principles and Literary Appreciation. A melodramatic play is based on:

A melodramatic play is based on sensational plot and characters. Melodrama is a genre of drama characterised by exaggerated emotions, stereotypical characters (clear-cut heroes and villains), and sensational, often implausible plot lines designed to appeal directly to the audience's emotions.

The typical melodrama features dramatic twists, moral extremes, and heightened situations: virtuous characters suffer at the hands of villains, and justice ultimately prevails in a way that maximises emotional impact. Characters tend to be one-dimensional - the hero is purely noble, the villain is purely evil - rather than psychologically complex.

"A melodious manipulation of events" is based on a false etymology. Although "melodrama" does derive from the Greek melos (music) combined with drama, historically referring to the musical accompaniment that underscored emotional scenes, the genre is not defined by "melodious" plotting. "Ingredients that mellow down events" describes the opposite of melodrama, which intensifies and heightens events rather than softening them. And while some plays may carry didactic overtones, didacticism is not the defining basis of melodrama as a genre.