Most congregations use the upper notes whenever the Ten Commandments are read – on Shavu’ot and Parashat Yitro and Parashat Va’et’channan. The custom of many synagogues in Jerusalem is to keep the upper notes for Shavu’ot and not use them on the two regular Shabbatot we have mentioned.
From the theological point of view the difference between the two melodies echoes the question of how special the Ten Commandments are – are they unique and pre-eminent, or merely part and parcel of the whole range of Jewish law?
The argument for the first option is that these are the fundamental principles of Judaism; the second option insists that all the 613 commandments are sacred and binding. Maybe the problem was caused by early Christianity, which said that only the Decalogue came from God and has eternal and binding status (though in that case why did the Church move the Sabbath from the seventh day?) whilst the other commandments were given through angels as a punishment for human sinfulness.
Regardless of this history the discussion reflects a problem that divides the Jewish people into those who proudly claim, “I keep the Ten Commandments!” but ignore most of the others (plus some of the Ten Commandments themselves), and those who humbly try to live by the whole pattern of Jewish observance. Ten-Commandments-Jews deserve some credit, but they leave out – and lose out on – so much.