Question: Which singer is also a guitarist, Kang Seung-yoon or Piotr Wiwczarek?
Sentence (from "Piotr Wiwczarek"): Piotr Wiwczarek (born 22 October 1965 in Olsztyn, Poland), also known as Peter, (ex nickname Behemoth) is a Polish guitarist and vocalist who is the frontman for the death metal band Vader, as the only constant member of the band since its inception.
Relevant evidence: Yes