Complex sentence: Twenty eight years after the release of their last album Coney Hatch regrouped, keeping a promise made to Carl while he was in his coma: that if he survived they'd release a new album.
Split into simpler sentences: Twenty eight years after the release of their last album Coney Hatch regrouped, keeping a promise made to Carl while he was in his coma. If he survived they'd release a new album.