If a person is in the middle of shemoneh esrei and he hears:
- Kedushah: He should stop and listen to the chazzan saying “kadosh…”, “baruch…”, and “yimloch…”
- Kaddish: He should stop and listen from the beginning to “yisbarach.”
- Barchu: He should stop and listen to the chazzan and the tzibur’s response. He should even bow if he is NOT at the beginning or end of a beracha (unless it is the first berachah or modim).
- Modim: He should bow (according to the rules of the previous din.)
- Birkas Kohanim: He should stop and listen (if there are kohanim bentching).