When a Shiite prayer ringtone sounded out on a mobile telephone in Iraq’s parliament last year, a sectarian brawl ensued. The incident highlighted rising tensions over increasingly popular but controversial ringtones that feature sound bites of Koranic verse or audio clips of azan, traditional calls to prayer.

Muslim clerics are divided over the ringtones, which can be downloaded from a number of Web sites. In Lucknow, India, for instance, clerics recently issued a fatwa that forbids the ringtones, which they consider “un-Islamic.” Abdur Raheem Qureshi, a member of the conservative All India Muslim Personal Law Board, which interprets religious law for the country’s 150 million Muslims, defends the edict. “When Koranic verses are recited, it is incumbent on all Muslims to listen with rapt attention and full respect in their minds,” he says. That could be difficult when answering a call.

Other Muslim leaders, though, aren’t so sure. Across the border in Pakistan, clerics rejected a ban. “Using technology for the propagation and respect of religion increases people’s reverence,” says Muhammad Khalid Masud, chairman of Pakistan’s Council of Islamic Ideology, adding that the argument harkens back to the 19th century when Muslims debated gramophone recordings of the Koran.

But, today, technology is far more pervasive, and its reach is increasingly colliding with questions of faith. And sometimes, it’s clear the ringtones are meant to offend. Some Shiite militants, for instance, answer their phones to melodic strains of anti-Sunni diatribes. There’s certainly no Islamic virtue in...