The second sentence uses parallel structure because there are commas in appropriate places and when this sentence is read aloud is makes sense.
The high school band gave a concert that lasted for an hour.
The fights between Mercutio and Tybalt and then between Romeo and Tybalt are chaotic; Tybalt kills Mercutio under Romeo's arm, flees, and then suddenly, and inexplicably, returns to fight Romeo, who kills him in revenge. Passion outweighs reason at every turn.