Complex sentence: Not long after that, however, artistic disagreements caused singer André Matos to leave Viper to start his own band, Angra; rather than looking for another singer, bassist (and main composer) Pit Passarel took over the microphone.
Split into simpler sentences: Not long after that, however, singer André Matos left Viper and later started his own band, Angra. Rather than look for another singer, bassist (and main composer) Pit Passarel took over the microphone.