The Sages prohibited playing instruments on Shabbat and Yom Tov, lest the instrument break and the player fix it, thus violating Torah law (MT 23:4). In contrast, in the Temple, rabbinic Shabbat prohibitions (shvut) did not apply; therefore, even on Shabbat and holidays, the Levites would accompany offerings with flutes, harps, lyres, trumpets, and cymbals (Beitza 11b).
Included in the prohibition of playing musical instruments is the prohibition of blowing a shofar. Even on Rosh Ha-shana, once the mitzva of shofar has been fulfilled in the optimal and most beautiful fashion, we do not blow further. Children under the age of bar mitzva may blow the shofar all day on Rosh Ha-shana so that they can learn how to do it (Rema 596:1; MB 3-5).
One may produce sound that is not musical in nature. Thus, one may clap his hands to wake someone up, knock on a door with his hands or an instrument so that the people inside will hear and open up, or tap a glass or bottle with a spoon to quiet a crowd. One may also snap in order to wake someone up or to make a baby laugh (SA 338:1).
The poskim disagree whether one may use a door knocker or mechanical bell. Some forbid it on the grounds that it resembles a musical instrument too closely (Rema). Others permit it since one is not trying to make music (SA 338:1). If during the week an electric doorbell is used, then on Shabbat a mechanical doorbell or knocker may be used (MB 338:7).
One may place a decorative crown with bells on a Torah scroll even though the bells produce sound. Since they are decorative and honor the Torah, it is for the sake of a mitzva, and since the person carrying the Torah does not intend to make noise, it is not forbidden (Shakh and MA, as opposed to Taz).
Some forbid opening a door that has bells or chimes attached to it, since they are considered musical instruments (Taz and Eliya Rabba). Others permit it, because those entering do not intend to make noise, they just want to open the door (MA). Le-khatĥila, it is proper for homeowners to remove bells from the door before Shabbat; if they did not do so, the door may still be used (see MB 338:6).
One may whistle on Shabbat because it is considered a type of music made with the mouth, not with an instrument. Some even permit using one’s fingers to improve the whistle (AHS 338:7; see below in 24:7 about toys that make noise).
. Eruvin 104a records a disagreement about this issue. According to Ula, one may not produce sound on Shabbat even without intent to make music. Therefore, one may not knock on the door so that the people inside will hear him. Rava maintains that only producing sound with the goal of creating music is prohibited. The Yerushalmi tells the story of R. Ila’i, who returned home on Friday night and called out to the members of his household to let him in. They did not hear him. Since he was personally stringent not to knock, he slept outside (y. Beitza 5:2). Indeed, Rabbeinu Ĥananel and the Vilna Gaon rule in accordance with Ula’s strict approach. In any case, even according to them, knocking with a shinui is permitted (BHL 338:1 s.v. “aval”). However, based on the subsequent discussion in the Gemara, Rif and Rambam (MT 23:4) conclude that the law is in accordance with the lenient approach of Rava. Rosh is inclined to follow this as well. Almost all the poskim follow the lenient approach, including SA 338:1, MB ad loc. 2-3, and SSK 28:41. However, regarding a door knocker, an instrument designed to produce sound, Maharil is stringent. Beit Yosef suggests that Maharil’s stringency is due to the concern that the person knocking may in fact intend to produce music. Rema 338:1 is stringent, following Maharil. According to BHL 338:1 s.v. “ho’il,” this is the position of SA as well. However, Livyat Ĥen §110 and Or Le-Tziyon 2:39:1 argue that according to SA, one may use a door knocker. If the knocker is meant to be used only on Shabbat, then Rema permits it as well (MB 338:7; Shevet Ha-Levi 9:76). Therefore, one may use a mechanical doorbell on Shabbat if an electric one is used during the week (SSK 23:55 with n. 159).A ĥazan may not use a tuning fork to help him determine the pitch for his singing, because it is included in the prohibition on musical instruments (MB 338:4). While some are permissive, since a tuning fork produces a sound that is uniform and relatively quiet, and it is being used for the sake of a mitzva, it is proper to be stringent, because that is the opinion of almost all the poskim. If one wishes to rely on those who are lenient, it is not necessary to object (AHS 338:8; see Yabi’a Omer 3:22).