There has to be chemistry in a duet, but if you go beyond the point of friendship and attraction, you lose something.

This quote means that when singing a duet, it is important to have a connection between the two singers, but if they become too close, they risk losing some of their performance quality. It is important to have chemistry in singing a duet, as this helps the performance come alive, but having too close of a relationship between the singers can take away from the performance, as it may take away from the focus or energy that the singers have for their performance.