We will begin our discussion with the main sources before moving on to practical considerations.
The gemara[2] criticizes the manner in which the people of Yericho would recite Shema. Rabbeinu Yona[3] explains that they did not read it calmly, “with its te’amim,” which the Tur[4] understood as referring to its trop, thus indicating that it is proper to say Kri’at Shema with its trop. The Beit Yosef[5] questions whether the Tur understood Rabbeinu Yona correctly, considering also that few people in his time read Kri’at Shema with the trop, and suggests that Rabbeinu Yona simply meant that one should be careful to pause at the right places so that the text is properly comprehensible. Nevertheless, in his Shulchan Aruch,[6] he accepts the Tur/Rabbeinu Yona’s idea that using the Torah trop is a requirement, although it is clear that b’di’eved one fulfills the mitzva without it. (It is interesting to note that the question of whether the trop is of Torah origin or was added at some later time is subject to machloket.[7])
On the Ashkenazi side, the Rama also discusses the matter, but with slight differences between his two major works. In his Darchei Moshe,[8] he writes that for many people, reciting Kri’at Shema with the trop is liable to detract from their concentration. He further reports that the minhag is not to use trop. He views the practice as positive only for those who are confident that they are able to concentrate on the content and the trop at the same time. In his glosses on the Shulchan Aruch, however, the Rama is slightly less selective and notes, “In our countries, this is not the minhag. However, those who are exacting are stringent on the matter.”
Is there anything other than concentration that one may lose by using the trop? The Ishei Yisrael[9] implies that a mistake in the trop is liable to change the meaning of the pasuk, which requires one to go back and recite it correctly, just as in the case of kri’at haTorah,[10] and this might unnecessarily complicate matters. On the other hand, the same problem arises if one reads Kri’at Shema without the trop but recites it with incorrect punctuation.[11] The type of reading that is more likely to cause punctuation problems probably depends on the person. If one reads Shema at a mainly uniform pace, then even if his reading does not emphasize the correct meaning, he also does not reinforce the wrong meaning, unless he does not pause at all at major stopping places (classically, where there is a sof pasuk or an atnachta). Thus, reasonably accurate laining is likely to improve much of the comprehensibility, but mistakes could sometimes make things worse than reading simply at a uniform pace.
Other issues emerge if one reads audibly with the trop. One issue is yohara – i.e., the other daveners will view it as haughty if an individual reads in a manner giving the impression that he considers it a “better way” than the local minhag.[12] The other is that laining has a tendency to disturb the concentration of people around the lainer. While the major application of the issue of disturbing others applies during Shemoneh Esrei,[13] when people are especially silent and need total concentration, it could apply here as well.[14]
Some have a reasonable practice of using trop just for the first parasha, which, according to some, is the only part whose obligation is from the Torah.[15] However, paradoxically, the first pasuk, which in some ways is most important,[16] may not be the place to use trop. Its pace is meant to be uneven,[17] since some of the words are pronounced at a slow speed or with great intensity,[18] and this is more difficult to do with trop.