Q. When repeating the amida, Halacha requires that we must have at least nine people listening to the shaliach tzibur and answering amen to his brochos. Since in our days it is unusual for someone to maintain constant attention that long, should the shaliach tzibur, better have in mind to daven a tefilas nedavah or an added voluntary amida when repeating aloud the shemone essre, especially when the minyan is exact or small?
A. Shulchan Aruch (O.H. 124: 4) rules that when the shaliach tzibur repeats the amida, the present should be silent while paying attention to the brochos being recited and answering amen to them. If there are no nine people listening, it is close to consider the blessings as recited in vain.
Mishna Berura (ibid. 17- 18) maintains that one should not recite other tefilos or learn at that time, but carefully listen to the complete brocho being recited. When not enough are listening, he quotes Shulchan Shleima, that suggests the shaliach tzibur making by his own a condition that if nine are not listening, his amida repetition should be an added voluntary amida.
Since the Shulchan Aruch (55) ruled that if there were ten present at the very beginning of the amida and then some left, one may continue the repetition, some Poskim argue that after the fact, if nine listen just to the first brocho, or at least to the beginning of that brocho, it is only close to being a blessing in vain. However, if no six individuals are paying attention, when repeating the rest, it would certainly be in vain. (Pischei Teshuva, Igros Moshe 4: 19).
Horav Shlomo Miller’s Shlit’a opinion is similar.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a