Complex sentence: Keen will be the newest Highway 65 artist, that Rayna promises to help strip down's sound, but when he realizes how much the label needs his album to be a hit, he begins to control Rayna.
Split into simpler sentences: Keen will be the newest Highway 65 artist, and Rayna promises to help him strip down his sound. When he realizes how much the label needs his album to be a hit, he begins to control Rayna.