Complex sentence: Avenged Sevenfold emerged with a metalcore sound on their debut "Sounding the Seventh Trumpet" but their style had evolved by their third album and first major label release, "City of Evil", into a heavy metal and hard rock style.
Split into simpler sentences: Avenged Sevenfold emerged with a metalcore sound on the band's debut "Sounding the Seventh Trumpet". However, Avenged Sevenfold's style had evolved by the band's third album and first major label release, "City of Evil", into a heavy metal and hard rock style.