For the next few weeks, instead of writing on the weekly Parasha I will be writing a series of Halachic (Jewish ritual law) pieces. Although they feature a technical and legalistic style, their focus is on the conceptual underpinnings of the topic. As always, feedback is appreciated in the comments – and thank you for reading.
With the increased amount of singing in shul on Shabbat and Yom Tov, an issue often arises for the chazzan and the congregation. What should be done when the text of the Siddur does not quite fit with the length of the tune that they wish to sing? Is it ever permissible to repeat words or phrases in the prayer service for the sake of properly enjoying an uplifting tune? There are many synagogues that allow this leeway during their services. Are they doing the right thing? Are different sections of the siddur treated differently? This first of a series of articles will address these questions.
One consideration that is relevant to repeating parts of prayers is the need to maintain the integrity of the Siddur liturgy. The Siddur contains two types of prayers: prayers that are part of a formal, set text, and those that are customarily recited along with them. Set prayers include all brachot and Shemoneh Esrei, while a customary prayer would be Aleinu or Adon Olam. The prayers that are a set part of the liturgy were canonized by the ancient Rabbis as part of the Siddur and given special status with their own set of laws. These laws do not, however, apply to the parts of the service that are merely customary. Among these laws is the restriction on interrupting the recitation of these prayers in any way, especially by talking. Depending on the nature of such an interruption, it is sometimes necessary to repeat the entire passage over again from the beginning to correct it. According to R. Moshe Feinstein (O.C. 2:22), when words of a prayer are repeated out of their original context and relocated to a different part of the prayer, they are considered such an interruption and necessitate repetition of the entire passage (if they meet the criteria mentioned in the note). An example of this would be the repeated repetition of a word or short phrase to serve as a type of chorus at several locations in a prayer. If, however, the word or phrase is repeated while maintaining its original context and position, it is not considered an interruption and does not interfere with the validity of the prayer. For example, the final three words of a sentence are repeated to compensate for a stanza that is too short for the entire tune. Since this repetition is being carried out unnecessarily, e.g. to enhance the beauty of a tune, although it is not prohibited it is nevertheless improper and frowned upon. Perhaps this is because although such a repetition would not violate the restriction on interruptions, it nevertheless compromises to some extent the sacrosanct nature of the Siddur and its liturgy. In contrast, a prayer that is merely customarily part of the Siddur would not be subject to these restrictions and its words or phrases could be freely repeated in their original context or even in others to enhance its melody.
Next time we will introduce special considerations that must be taken into account regarding the repetition of parts of verses from Tanach.
 If an interruption is either deliberate or changes the meaning of the prayer, that prayer must be recited over again from the beginning. If however, an interruption was spontaneous or if it did not change the meaning of the prayer, although it is no longer ideal the prayer may be completed as is.
 If this repetition is carried out for a constructive purpose like rectifying a lack of sufficient intention during the original recital, it is permitted.