May the Congregation Join The Hazzan Singing The Kadish?

Often, on Shabbat and Yamim Tobim, the Hazzan sings the Kaddish in a melodious tune, and in some synagogues, the congregation joins the Hazzan's singing. The Kaf Ha'haim (Rav Yaakob Haim Sofer, Baghdad-Jerusalem, 1870-1939) writes that this is improper. The Kaddish is only for the Hazzan to recite; the congregation must listen silently and respond, without joining in the Hazzan's recitation.