Someone gave me a recording of the tefilos of Yom Kippur in a well known Yeshiva. The Baal tefila is no longer alive. The recording was made by a jew placing a modern digital recorder underneath the amud where the chazan stands before Yom Kippur. The recorder had a internal timer, it recorded from before kol nidrei to sometime after mariv, and again from before shacharis to the middle of neila, when the battery died. The chazan and all people in the room were unaware of the presence of the recorder. The recorder was owned by the Jew who placed it there. I was wondering what, if any, are the halachic issues Relevant here. Some people told me that it may be prohibited to listen to it.