[Take a look at this Haveil Havalim edition, linking to tributes to RivkA, a"h, of Coffee and Chemo]
I'm teaching a class Monday night on the Music of Jews in Arab Lands, and that will lead into the general question of the propriety of adopting secular music for prayer. Here are some of the sources I will use in the discussion; note that some of the sources are about general singing of secular tunes, and others are about prayer, specifically.
Responsa of Maimonides, 12th century Egypt, #224
A question from Aram Tzova: Is it permissible to hear the Hazor Arab songs?
The answer is known: The song and tunes are prohibited even without words, as we are taught, ‘The ear that hears music should be uprooted.’ The Talmud explained that there is no difference between hearing songs or playing on strings or hearing pleasant things without words; whatever causes joy and stirs a person is prohibited. They linked this to the prophet’s prohibition, ‘Do not be joyous, Israel, like the nations.’
The reason for this is very clear: One must conquer and prevent and rein in this desire, lest it become active and arouse him. We do not pay attention to the exception, of whom there are few, who is brought to greater spiritual care and intellectual awakening or humility before Gd [by this music]; the laws of Torah were written for the many and the normal…
We have already explained in our commentary to Avot that there is no difference between Hebrew and Arabic; the prohibition is based upon the content. In truth, one is prohibited from listening to stupidity even without song, and if it is played with instruments then there are three prohibitions – stupidity and obscenity, and verbal song, and song upon strings…
Responsa of Rabbi Yitzchak Alfasi, 11th century Morocco, #281
Regarding the synagogue chazan, of whom they have heard that he behaves improperly, such as singing Ishmaelite songs – should they remove him or not:
The leader who speaks improper words, such as vulgarity, singing Ishmaelite songs, should be removed. Regarding this it is said (Jeremiah 12:8), ‘She raised her voice upon me, and so I hated her.’
Rabbi Moshe Isserles, 16th century Poland, Darchei Moshe 53:10
A leader who acts inappropriately, such as speaking vulgarity, such as singing Arabic songs, should be subject to protest. Should he not listen, they should remove him.
Rabbi Chaim Palaggi, 19th century Turkey, Kaf haChaim 13:6
Would that they would warn poets and singers not to sing Kaddish and Kedushah in the garb of the nations, with the maqam. One who knows it will come to bad thoughts, and so the leader sins and causes others to sin. This is an offering with inappropriate intent, and it will not be acceptable. That which is impure cannot enter the hall of Gd, and its presence causes goodness to be absent. Regarding this it is written (Psalms 39:4), ‘Fire burns when I speak.’
Rabbi Yisrael Moshe Hazan, 19th century Rome, Krach shel Romi 1
Music, even that which is dedicated for idolatry, may not be compared to a [worshipped] monument [which the Torah forbids as a Canaanite practice]… Music itself is the essence of worship, as it is written, ‘And our lips will complete our bulls.’ This is prayer with humility and a pleasant voice and joy and trembling, with glory and beauty in the house of our Gd! If the sound they use when making music in the house of their idolatry is the sound which introduces humility into the heart, with its type of music and what people are accustomed to hearing… Could it be believed that because fools corrupted it and established it in the house of their prayers, we would be prohibited from using something our nature requires, one of the body’s five senses?!... In that case, we should also prohibit the cup of wine from havdalah, since they bless upon the wine of their libations in their churches!...
Rabbi Ovadia Yosef, 20th-21st century Egypt - Israel, Yabia Omer 6:Orach Chaim 7:3
Leave Israel be; if they are not prophets, they are descendants [‘students’] of prophets, and their custom is Torah.