another point is that you (the recommender, and, incidentally, also the user) are happy if there is at least one novel and interesting item in the recommendatio

another point is that you (the recommender, and, incidentally, also the user) are happy if there is at least one novel and interesting item in the recommendations. This might apply less to music (list) recommendations, but in general that's how I (as a customer) also approach lists of recommendations.