The plot of La Forza del Destino is set in Spain and Italy around 1750.
Don Alvaro (from South America) has arrived in Seville and fallen in love with Donna Leonara, who is the daughter of the Marchese di Calatrava. The Marchese has forbid their union, but they plan to escape. When they go to leave, the Marchese discovers them – Alvaro throws down his pistol to show he is surrendering it, but it goes off and kills the Marchese, who dies uttering a curse upon them. They go their separate ways.
A summary of the plot can be found here: https://www.metopera.org/discover/synopses/la-forza-del-destino/
The ‘rataplan’ in this chorus is designed to replicate the sound of a snare drum, and the final ‘pim’ is the signal to fire the rifles.
The music, including the orchestra intro, is based on triads and broken chords, with a long solo melody by the fortune teller Preziosilla.
The Listening Project Blog 