Rolf Köhler, Detlef Wiedeke and Michael Scholz are Systems In Blue, a german group that continue with the sound of 80's in a Modern Style. They were part of the chorus of some Dieter Bohlen Productions like Modern Talking and Blue System, replacing and helping the voice of the same Dieter Bohlen in many songs.

http://en.wikipedia.org/wiki/Systems_in_Blue
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