Arctica are primarily Kim Stanley and Lloyd Cox. They record songs made up on the spot, with a microphone hanging from a lightbulb in a 100% improvised fashion. Nothing is taken away or censored and what you hear was completely created in the moment with no beforehand thought or writing.
On hugely rare occasions, Arctica play live with the assistance of Loz Hancock(drums) and Michael Gammon(bass). When they play live it is completely improvised, aided by a few scale discussions.