Chazarat hashatz is a logical time to take care of planning the aliyot. Although it is theoretically better to do so as the Torah is being taken out of the ark, practically, this would often not leave enough time.
The Shulchan Aruch[3] writes sternly about one who engages in “mundane talk” during chazarat hashatz, which implies that matters of an appropriate nature are permitted. This does not mean that one should feel free to do any positive act (e.g., learning) during chazarat hashatz; as a rule, people should listen, be careful to answer amen to the berachot, and not affect negatively the discipline of others in shul.[4] However, everyone should understand that a gabbai has little choice but to use that time to carry out his communal tasks. (It is unfortunate that some gabbaim take the opportunity to also do unnecessary “schmoozing.”) Exceptions during chazarat hashatz are when there may not be ten people,[5] besides the gabbai and the person with whom he is speaking, who are following chazarat hashatz[6] and during Kedusha[7] and Modim D’Rabbanan. Speaking during Kaddish is more severe than during chazarat hashatz and should be avoided at almost all costs.[8]
The more difficult question regards the various parts of kri’at haTorah. The gemara in Sota[9] says: “Once the sefer Torah is opened, it is forbidden to speak even in matters of halacha.” The gemara in Berachot,[10] however, mentions that Rav Sheshet learned during kri’at haTorah. To reconcile these sources, the Rishonim make various distinctions pertaining to who the learner is and what his circumstances are.[11] Nevertheless, according to at least most of them, it is forbidden for a gabbai to speak during the actual laining. This could be because it is disrespectful or disruptive or because he is missing sections that he should hear.[12] Only in a situation in which there is no choice would talking be permitted at this time.[13]
There is a machloket regarding whether it is permitted[14] or forbidden[15] to speak divrei Torah[16] bein gavra l’gavra (between aliyot). The Beit Yosef objects, but out of a somewhat technical concern that one who begins to speak might not stop in time for the next aliya. This concern does not seem to apply strongly to a gabbai on duty for two reasons: he needs some latitude in order to do his job and the laining will generally not commence until he is ready.
A remaining question regarding kri’at haTorah is how to view the beracha after an aliya.[17] Is it considered part of the laining, to which everyone must listen, or is it part of bein gavra l’gavra? The Ritva[18] says that the fact that the concluding beracha begins with “Baruch” indicates that it is not a “continuation beracha,” and one may therefore talk before it is recited. In a similar vein, regarding the halacha that one may leave shul bein gavra l’gavra, the Pri Chadash[19] says that the period after the reading but before the beracha is already considered bein gavra l’gavra. Some rabbis even had the minhag to deliver a derasha before the ending beracha.[20] In addition, there is significant discussion regarding whether the berachot are an obligation for the whole congregation or just for the oleh and whether it is important for ten people to hear them.[21]
After weighing these factors, it seems reasonable to conclude that if (1) ten people hear the beracha, (2) the gabbai can talk without distracting the oleh, and (3) it will help eliminate delays that burden the congregation,[22] then the gabbai may speak in order to fulfill his responsibilities before or during the oleh’s concluding beracha. Others should listen to the beracha intently.