Complex sentence: The band have been active underground since the Early 90s, with Sven de Caluwe as a singer from 2002 to 2004, when he left to focus on Aborted; he was replaced by Swedish singer Mike Löfberg from Blockhead.
Split into simpler sentences: The band have been active underground since the Early 90s, with Sven de Caluwe of Aborted as a singer from 2002 to 2004. He was replaced by Swedish singer Mike Löfberg from Blockhead.