A shaliach tzibbur kavua has begun to incorporate tunes from secular sources in the Shabbos davening. For example, he sang kedushahto a popular broadway song. Some people sang along and enjoyed the innovation, but others claimed that he was bringing the theatre into shul, and fiercely objected. Are there halachic sources on this matter?
Rav Ovadya Yosef (Yecheveh Daas II, no. 5) is in principle lenient concerning this matter, yet states that it is preferable for a chazan to use tunes associated with kodesh songs (even if their original source is some long-forgotten secular song), which will prevent people from thinking of the secular songs and their improper words and associations.
However, Rav Yaakov Moshe Hillel (Vayashav Hayam, II, no. 7) writes extensively that it is prohibited to bring secular songs into the holy shul, stating that the practice is included in the ruling of Rema prohibiting songs of avodah zarah, and quoting from letters written him by Rav Shmuel Wosner and by Rav Noson Gestetner (who both prohibited the practice), adding that only those songs whose source secular has been forgotten are permitted.
It is interesting to note that Likkutei Muharan (I, 236) writes that using secular songs for kodesh is a worthy practice, in particular on Shabbos, because it elevates the tunes from tumah to taharah. However, his words have not been quotes by poskim (they do not take into consideration the improper thoughts that may be caused by using secular tunes, and it is possible that he would not have made the statement concerning well-known tunes).
Of course, if the congregation (or a significant part of it) is against the practice, then it would be wrong to use the tunes.