Shir Shel Yom on Rosh Hashana and Yom Kippur
In most congregations, the daily Shir Shel Yom is moved from its usual place at the end of the service and is recited at the beginning of the service on Rosh Hashanah and Yom Kippur. There is actually no clear or authoritative reason why this is so, but a number of theories and explanations have been offered.
One explanation for the change is that it is in order not to burden the congregation with a seemingly unimportant reading at the conclusion of an already long prayer service. The problem with this approach, however, is that it is just not true. The service will end at the same time whether a certain prayer is recited at the beginning of the service or at the end. Would the sages implement such a change simply in order to create some kind of childish psychological diversion? Maybe, but unlikely.
Nevertheless, moving the Shir Shel Yom to the beginning of the service does create the impression that the service is shorter and such an adjustment does have some precedent. Indeed, it is suggested that the custom of reciting bameh madlikin Friday nights before maariv, rather than after maariv, and the custom of reciting Hoshanot on Sukkot after Hallel rather than after Mussaf, were both implemented in order to create the impression of a less drawn-out service.
There is also a theory that the Shir shel Yom was moved to the beginning of the service due to a concern that people might rush out after services – or even before they are formally concluded -- and opt to skip the “less important” parts of the service, such as the Shir shel Yom. Similarly, it is also noted that the Mourner’s Kaddish is recited after the Shir Shel Yom. As such, perhaps it was moved to the beginning of the service in order to pressure those with an obligation to recite Kaddish to come on time for services.
The sefer Shirat Shmuel, which is a compilation of everything imaginable on the topic of the Shir Shel Yom, also ponders this question with no concrete answer. He suggests that perhaps the Shir Shel Yom is recited at the beginning of the service, alongside the korbanot, in order to further emphasize the avoda in the Beit Hamikdash, a theme that features prominently in the Rosh Hashana and Yom Kippur liturgy. This is because the Shir Shel Yom was a vital component of the daily sacrificial service in the Beit Hamikdash which the recitation of korbanot is intended to recall. While this latter explanation is a slightly more plausible one, it is still problematic. This is because it is not merely the Shir Shel Yom that is moved to the beginning of the service, but a number of other additional readings, such as the shir hayichud and anim zemirot that are moved to the beginning of the service, as well. These readings have no apparent connection to the Beit Hamikdash.
Perhaps the Shir Shel Yom is recited at the beginning of the service on Yom Kippur because, unlike on Shabbat and all other holidays, the Yom Kippur mussaf ends abruptly with the full kaddish. All the other routine end-of-service readings are recited at other points in the Yom Kippur prayers or are omitted entirely. Another possible explanation, albeit a weak one, is that the Shir Shel Yom is recited earlier on Rosh Hashana and Yom Kippur in order to delay the start of the Mussaf service. It is preferable not to recite Mussaf -- on Rosh Hashana at least -- before the third hour of the day.
My friend, Jerry Glazer of Modiin, suggests that maybe the Shir Shel Yom was moved to the beginning of the service in order to recall that the Leviim in the Beit Hamikdash were required to sing the Shir Shel Yom by a certain time each day. This is a great explanation considering that the Shir Shel Yom was sung as part of the daily Shacharit service whose deadline was chatzot, noon. The Rosh Hashana and Yom Kippur services generally end far past this time. Therefore, perhaps the Shir Shel Yom is recited at the beginning of the service in order to ensure that it is recited before the chatzot “deadline.” I later found the same explanation given by Rav Ephraim Greenblatt.
It might just be, however, that the widespread practice of reciting the Shir Shel Yom at Mincha on Tisha B’av, rather than at Shacharit, throws a monkey wrench into this theory. If reciting the Shir Shel Yom before chatzot each day is so important then it should be recited before chatzot on Tisha B’av, as well! Howie Bryks of New Rochelle, however, suggests that reciting the Shir Shel Yom at Mincha on Tisha B’av may not be such a monkey wrench, after all. He suggests that perhaps it is recited at mincha on Tisha B’av because it is something too joyous to be recited on Tisha B’av morning.
It should be noted that the Noheg K'tzon Yosef records a custom of always reciting Shir Shel Yom at the beginning of the service together with the korbanot. This actually makes good sense considering that the Shir Shel Yom was sung as part of the morning service in the Beit Hamikdash that the daily recitation of korbanot serves to recall. However, I don’t know of any community that follows this custom on a regular basis, and it is nearly impossible to suggest that the source for doing it on Rosh Hashana and Yom Kippur is based on the Noheg K'tzon Yosef, as it is a work of primarily German customs. It is also not a sefer that commands much halachic authority.
 Aruch Hashulchan, OC 584:1.
 Rivevot Ephraim 1:399.
 Avoda Zara 4b; OC 591:8; Aruch Hashulchan, OC 591:13; Mishna Berura 591:13-15.
 Erchin 11a; Tur, OC 237.
 Rivevot Ephraim 1:399.
 Noheg K’tzon Yosef p. 42.