When listening to Koops music, it's somehow easy to believe that it's played by a small orchestra, but in fact the music is based on samples. Thousands of small clips from records puzzled together into new songs. All the drums, strings, horn sections and choirs are actually sampled! This is a very time consuming way to make music (it's one of the reasons it takes such long time to make a Koop album), but it's the only way to create the surreal Koop sound.
One thing though, that for sure aren't sampled, is the vocals. Many singers has blessed the Koop albums with their talent, and on Koop Islands the singers are: Ane Brun, Yukimi Nagano, Hilde Louise Asbjornsen, Rob Gallagher and Mikael Sundin.