Gemara

(Mishnah): After the Sanhedrin was abolished, song was abolished from drinking houses - "they will not drink wine with song."

(Rav Huna brei d'Rav Yehoshua): We learn from "elders ceased from the gate, youths from their singing."

(Rav): An ear that hears song deserves to be cut off.

(Rava): If there is song in a house, its end is to be destroyed - "a voice singing in the window, destruction is in the Saf (doorway)..."

(Rav Huna): The songs (sung while working) of those who pull ships by ropes, and of plowers, are permitted. Songs of weavers are forbidden.

Rav Huna abolished song. Prices dropped. One could buy 100 geese or 100 Sa'im of wheat for one Zuz, and no one was buying! Rav Chisda came and did not protest against song. A goose could not be found for one Zuz.

(Rav Yosef): If men sing and women answer, this is lewd. If women lead and men answer, lust flares like burning chips of flax.

Both are forbidden. If one cannot stop both, he should prevent the latter.

(R. Yochanan): Anyone who drinks amidst music of four types of instruments brings five punishments to the world - exile, famine, that Torah will be forgotten, weakening of the enemies of (a euphemism) Hash-m, lowliness of Yisrael. We learn from "... lyre and harp, tambourine and flute, their drinking sessions of wine... Therefore, My nation will be exiled...

Gitin 7a - Question: What is the source that song is forbidden?

Answer (Mar Ukva): "Do not rejoice Yisrael, do not rejoice like the nations."

Question: Why didn't he answer "they will not drink wine amidst song; strong drink is bitter to those who drink it"?

Answer: From that verse, one might have thought that song with instruments is forbidden, but vocal song is permitted. Mar Ukva teaches that this is not so.

Sanhedrin 101a (Beraisa): If one reads a verse of Shir ha'Shirim as if it were a song, or reads verses in the pub out of place (just for fun), he brings evil to the world. The Torah girds itself in sackcloth and complains to Hash-m 'Yisrael treat me like a harp for scoffers to play'!

Hash-m: When Yisrael eat and drink, in what should they engage?

The Torah: One who learns Mikra (Tanach) should learn Mikra. One who learns Mishnah should learn Mishnah, Halachos and Agados, one who learns Talmud should learn what is relevant to the season, e.g. laws of that festival.

Rishonim

Rif and Rosh (Berachos 21b and 5:1): A Gaon explained that vocal song is forbidden, i.e. love of people or praising beauty. No Yisrael refrains from songs and praises of Hash-m and recalling His Chasadim. All of Yisrael sing these joyously in wedding halls and pubs. We never saw anyone protest about this.

Rambam (Hilchos Ta'anis 5:14): They decreed not to play musical instruments. One may not rejoice in or hear all kinds of song and instruments, due to the Churban - "they will not drink wine amidst song." The custom of all of Yisrael is to say praises of Hash-m or songs of thanks to Him and similar matters over wine.

Beis Yosef (DH u'Mah she'Chosav Rabeinu umi'Lashon): The Rambam forbids instruments in every case. Vocal song is forbidden only over wine.

Poskim

Shulchan Aruch (OC 560:3): They decreed not to play musical instruments and all kinds of song and everything that produces sounds of song for enjoyment.

Mishnah Berurah (11): This opinion forbids instruments even not over wine.

Rema: Some say that this is only for one who is used to this, e.g. kings who rise and lie down amidst song, or in the pub.

Sha'ar ha'Tziyon (23): Hagahos Rema on the Mordechai (Reish Gitin) says that the Isur is only when one only drinks, like Nochrim do, but not if he drinks with his meal. Perhaps one need not protest in such a case.

Shulchan Aruch (ibid.): It is forbidden to hear them due to the Churban. Even vocal song over wine is forbidden - "they will not drink wine amidst song."

Beis Yosef (DH v'Chosvu): Tosfos (Gitin 7a DH Zimra) forbids vocal song in pubs and similar situations. The Yerushalmi says so about one who rises and lies down amidst song; this is excessive.

Magen Avraham (8,9): In pubs, even one who does not usually do so is forbidden. The Tur says that in a Teshuvah, the Rambam forbids even without wine; the Bach rules like this. Why didn't the Shulchan Aruch say so? We permit songs of those who pull ships and of plowers, to make them work better, but not of weavers. Women may not sing while working.

Mishnah Berurah (13): If women will not heed us, it is better that they be Shogeg than Mezid. If men are around, it is a great Mitzvah to stop this.

Kaf ha'Chayim (30): When one fasts, especially the fasts over the Churban, he should intend that the fast atone for having heard forbidden music.

Shulchan Aruch (ibid.): The custom of all of Yisrael is to sing praise of Hash-m and recall His Chasadim over wine.

Mishnah Berurah (14,15): One may not sing "Odcha Ki Anisani" and other Piyutim for Simchah of camaraderie. The Torah girds itself in sackcloth and complains... However, it is a Mitzvah to sing in the Beis ha'Keneses on festivals. At a meal, one should sing only songs enacted for meals, e.g. of Shabbos. It is a big sin to sing Kadish at feasts, and all the more so to make fun of verses or Kadosh words. The Heter is only to recall His Chasadim.

Birkei Yosef (6): Ma'aseh Roke'ach forbids singing Kodesh songs to Nochri tunes. Maharam Di Lonzano permitted this, and did so in spite of protests.

Ha'aros on Birkei Yosef (1): The Mishnah Berurah (53:82) forbids only tunes of idolatry. Certainly one may not sing Kodesh words according to tunes that Ba'alei Teshuvah recognize to be songs of passion. It disgraces the Kodesh, and reminds the Ba'alei Teshuvah of Tamei songs. If no one knows the Nochri words, it is permitted. We find that tunes of Kehilos of Yisrael are drawn after those of the lands they live in.

Eshel Avraham (9): Chazanim who sing Nigunim without words should be rebuked.

Note: The Mishnah Berurah (125:1) does not raise objections to this practice.

Kaf ha'Chayim (29): Women may sing to calm a baby. Shelah and Sifrei Musar forbid songs of passion, for it breeds a bad nature in the child. In any case it is forbidden, for it arouses one's Yetzer Ra. One should warn his household to distance from this.

Rema: Similarly, for the needs of a Mitzvah, e.g. in the house of a Chasan and Kalah, everything is permitted.

Beis Yosef (ibid.): The Tur (Siman 338) permits telling a Nochri to play music at a Chupah on Shabbos. Mid'Rabanan, one may not tell a Nochri to do things forbidden for Yisrael. It is permitted for the needs of a Mitzvah. There is no Simchah of Chasan and Kalah without music.

Beis Yosef (DH Garsinan): Those who pull ships sing to make them work zealously. Plowers sing to make the cattle, who like the song, go in the furrow. Songs of weavers are forbidden, for they are just for frivolity.

Magen Avraham (11): One should not rejoice too much.