The Shulhan Aruch (Orah Haim 494) rules that on Shabuot we read the section in the Torah that contains the Ten Commandments (in Parashat Yitro). The Be’ur Halacha (by Rav Yisrael Meir Kagan of Radin, 1839-1933), in this context, notes the two different sets of Te’amim (cantillation notes) that exist for the Ten Commandments. (There are also different versions of the actual text of the Ten Commandments – one in Parashat Yitro, and one in Parashat Va’ethanan; we deal here with the different versions of the Te’amim, not of the text.) If we open to the text of the Ten Commandments in Parashat Yitro or Parashat Va’ethanan in most printed Humashim, we will find the version called "Ta’am Tahton." The second version, which is called "Ta’am Elyon," is generally printed in the back of the Humash or after the Parasha.

What is the difference between these two versions?

One who looks at the text of the Ten Commandments in a Torah scroll will notice that the Torah assigns a separate paragraph for each commandment. Even the very short commandments, such as "Lo Tirsah" and "Lo Tinaf," comprise an independent paragraph, as do the longer commandments, such as "Lo Yihiye" and "Zachor." The "Ta’am Elyon" system of cantillation notes follows this arrangement, and makes each commandment no more and no less than a single verse. This means that the longer commandments are made into a single verse despite their length, and the short commandments, such as "Lo Tirsah" and "Lo Tinaf," are assigned a brief, two-word verse. The exception to this rule is the first two commandments, which are combined into a single verse in the "Ta’am Elyon." The reason for this exception is that, according to tradition, when God proclaimed the Ten Commandments, He uttered the first two commandments as a single statement. Therefore, even in the "Ta’am Elyon," which reflects the manner in which the commandments were heard at Sinai, the first two commandments are combined.

We refer to this system at the "Ta’am Elyon" (literally, "upper cantillaton") because generally speaking, the Te’amim that are used to extend a verse are the notes positioned on top of the word, such as the Pazer Gadol and Azla Geresh.

This system is used for the public Torah reading, whenever the Ten Commandments are read. Namely, on Shabuot, on Shabbat Parashat Yitro and on Shabbat Parashat Vaethanan, the Ten Commandments are read using the "Ta’am Elyon," so that they are read the way they were heard by the Jewish people at Sinai.

Although there is a tradition that a verse cannot be shorter than three words, we allow separate verses for the two-word commandments in the public reading, because this is how the Jews heard the proclamation of the Ten Commandments at Sinai.

The "Ta’am Tahton" system is used when a person reads the Ten Commandments privately, such as for the weekly "Shenayim Mikra Ve’ehad Targum" reading or for general individual learning. This system breaks up the text of the Ten Commandments according to the common, conventional length of verses. This means that the longer commandments, such as "Lo Yihiye" and "Zachor," are each divided in several verses, and the short commandments – "Lo Tirsah," "Lo Tinaf," "Lo Tignob" and "Lo Ta’ane" – are merged into a single verse.

The Be’ur Halacha notes that the different systems of dividing the text results in differences in the vowels sounds and punctuation of certain words. For example, if a word with a "Patah" vowel is situated at the end of a verse, the "Patah" is changed into a "Kamatz." (We generally pronounce the "Patah" and the "Kamatz" the same way, but in principle, they have slightly different pronunciations, and those who make a point of pronouncing words precisely indeed differentiate between these two vowels.) In the sixth commandment, "Lo Tirsah," the word "Tirsah" appears at the end of a verse in the "Ta’am Elyon," but in the middle of the verse in the "Ta’am Tahton." Therefore, under the letter "Sadi" of this word there is a "Kamatz" in the "Ta’am Elyon," but a "Patah" in the "Ta’am Tahton." There is also a difference between the two versions with regard to the pronunciation of the letter "Tav" at the beginning of the word "Tirsah." In the "Ta’am Elyon," the cantillation results in a "Dagesh" in the letter "Tav" of "Tirsah," whereas in the "Ta’am Tahton," the "Tav" is pronounced without a "Dagesh." This applies as well to the words "Tinaf," "Tignob" and "Ta’ane." Another difference affects the phrase "Ve’asita Chol Melachtecha" in the fourth commandment, the commandment of Shabbat. In the "Ta’am Tahton," this phrase concludes a verse, and thus for grammatical reasons there is a "Dagesh" in the word "Chol," such that it should be pronounced "Kol." In the "Ta’am Elyon," by contrast, this phrase does not conclude a verse, and therefore the word is pronounced "Chol."

One should be aware of these distinctions and ensure to use the "Ta’am Tahton" system when reading privately. And when one follows the public reading in the synagogue, he must remember to follow along with the "Ta’am Elyon" system, which, as mentioned, is generally found either in the back of the Humash or after the Parasha.