The Ba’al haMaor has a unique approach to understanding the whole concept of tekiyos d’meyushav. Unlike most Rishonim who read R’ Yitzchak’s question “Why do we blow sitting and then standing?” as referring to the tekiyos before mussaf (tekiyos d’meyushav) and tekiyos during mussaf, the Ba’al HaMaor says this cannot be R’ Yitzchak’s intent because in the days of Chazal there was no tekiyas shofar at all outside the context of tefillah. The proper kiyum of shofar is only possible within tefillah’s framework of malchiyus, zichronos, and shofaros, and therefore, claims the Ba’al haMaor, we never find in Chazal a formula of “..asher kideshanu b’mitzvosav v’tzivanu…” on tekiyas shofar – the brachos of tefila themselves serve as the bracha-context for shofar. R” Hershel Shachter elaborates on this theme in his sefer Eretz HaTzvi and writes that we find this with respect to other mitzvos as well: according to R’ Amram Gaon there is a brachas hamitzva on shema when said independently, but no birchas hamitzva required when shema is said in the context of birchos keriyas shema. This may be why there is no separate bracha on haggadah on leil Pesach – the mitzvah of sipur yetziyas mitzrayim occurs in the context of the other mitzvos of seder and therefore a unique birchas hamitzva being required. So what of our blowing before mussaf? The Ba’al haMaor claims this is a late minhag which developed because of the sick or inform who could not stay in shule until the completion of mussaf, which we daven late in the day on Rosh HaShana.
The Ramban in Milchamos vigorously disputes this Ba’al haMaor. Although there is a kiyum of tekiyos in the context of malchiyos, zichronos, and shofaros, this does not exclude the fact that there is a birchas hamitzva and a kiyum of shofar independent of tefillah.
When my kids were babies and needed my wife’s attention at home (which they probably still will) preventing her from staying through all of davening, I always thought this machlokes was relevant to deciding how to divide the time. Given the choice of being in shule for only part of daveing, would it be better to hear the tekiyos d’meyushav and probably miss some during chazaras hashatz, or better to hear the tekiyos of chazaras hashatz and miss the tekiyos d’meyushav (assuming you can reasonably schedule your kids one way or ther other)? According to this Ba’al haMaor, the ikkar kiyum is tekiyos al seder habrachos, during chazaras hashatz, not the tekiyos done earlier. But, things may not be so simple… stay tuned bli neder for more.