We have developed a method which allowed us to teach Grey Parrots special vocal patterns with a good success. The birds uttered these in antiphonal duets (Fig. 1, Table 1). The duets were performed only between the parrot and its cooperative partner. By experimental auditory stimulation we investigated the conditions of the vocal communication (Fig. 2, Fig. 3). Furthermore we found, that the performance of antiphonal duets obstructed the extension of the vocal repertoire with patterns which could not be learned from the birds' social partners (Fig. 4).