“I don’t know of a Kehilah that doesn’t sing liberally with the Chazzan throughout Chazaras ha’Shas of the Yomim Nora’im. Is this wrong l’Fi the Mishnah Berurah, or since the Minhag is to sing these words and only these words, perhaps there is no Cheshash that one will say the whole Berachah, and it is not Meichzi k’Yuhara?”
See Sha’arei Teshuva 582:7