Additionally, I've also mentioned my reaction to hearing multiple calls to prayer being heard simultaneously (see "Good-Bye J-Kart & Hello Bandung" and "Debrief Session"). In Christianity, the closest tradition for summoning worshippers is the ringing of church bells; a craft which is not at all common anymore. However, I do find the human voice to be a much greater and more complex instrument than the majestic bells. The music I used to accompany the video is "Call to Prayers" from the musical The Armed Man: A Mass for Peace by Karl Jenkins (previously referenced in the posting titled "The Armed Man").
Regardless of your personal religious persuasions, I do hope that you can enjoy the wonders of the Mosques of Indonesia.