Complex sentence: Helium were an American alternative rock band formed (as Chupa) in the summer of 1992 by Mary Lou Lord, Jason Hatfield (Juliana's brother), Shawn King Devlin (drums) and Brian Dunton (electric bass guitar).
Split into simpler sentences: Helium were an American alternative rock band formed in the summer of 1992. Originally calling themselves "Chupa", its founding members were Mary Lou Lord, Jason Hatfield (Juliana's brother), Shawn King Devlin (drums) and Brian Dunton (electric bass guitar).