For the segment class designation the temporal position of segments in two candidate segment classes is used for the stanza/refrain selection by means of a segment class designation means, wherein the highest-order segment class is designated as refrain segment class only when it has a segment following temporally later in the audio piece than the latest segment of the other candidate segment class. With this, segment class labeling with a low error rate is achieved, which can at the same time be implemented with easy effort and is further predestined for automated flow.