Zwetsloot brought a unique flavor to the band with his knowledge in classical music and theory helped the band form many of its dual harmonies. He was the rhythm guitarist while Nödtveidt played the harmonies as the lead guitarist.
The passage describes how Zwetsloot's classical music background and his role as rhythm guitarist contributed to the band's unique sound and harmonies. Nödtveidt, on the other hand, was responsible for the lead guitar melodies.