Question:  Hydra is an album by Within Temptation and contains guest appearances by an American metalcore vocalist best known for being the vocalist of what two bands?
Sentence (from "Hydra (Within Temptation album)"): The album contains guest appearances by singer Howard Jones (ex-Killswitch Engage), rapper Xzibit, metal vocalist Tarja Turunen (ex-Nightwish) and alternative rock singer Dave Pirner (Soul Asylum).
Relevant evidence: Yes