Egypt on Thursday began unifying calls to prayer that ring out five times a day from thousands of minarets across the capital, but the move has been criticised by the men who make the call or azzan.
The ministry of religious endowments says it will implement the plan neighbourhood by neighbourhood until all of Cairo's estimated 4,500 mosques transmit the call live and in unison from a radio station studio.
"It has so far been implemented without a problem in Nasr City and Heliopolis," ministry official Salem Abdel Galal said, referring to two of the city's neighbourhoods.
He said the unified call to prayer was supposed to start on Wednesday to coincide with the onset of the holy month of Ramadan, but that it was postponed for a day because of technical problems.
The calls to prayer, made by muezzins who are either paid small wages or volunteer for the task, are seldom issued simultaneously and sometimes drown out one another.
"The azzan should be done by those who are most qualified and have the best voices. But people who shouldn't be doing this are making the calls, and you hear some unacceptable noises," Galal said.
The plan has both won praise for reducing noise pollution and been criticised by others who feel its goes against tradition.
"This will put an end to the sound pollution generated by the microphones," said Suad Saleh, a professor of Islamic law at Al-Azhar University.
"At the time of the Prophet (Mohammed), only Bilal or one of his companions enjoyed the privilege of making the call to prayer. This decision will restore its true value and beauty."
But muezzins, who usually hold down other jobs and believe God will reward them for the task, complain they will lose a traditional vocation.
"The call to prayer is a true spiritual vocation. My voice is a gift from God. By putting it at his service, I thank him for the gift and I reaffirm my faith by calling others," said one muezzin, Sayed Abdel Rahman.
The five calls to prayer are made just before daybreak, at noon, in the afternoon, at sunset and in the night.
The lilting calls affirm basic Islamic tenets such as belief in one God and his Prophet Mohammed, and exhort the faithful to attend prayers. The dawn call adds that praying is better than sleep.
Explore further: Putting net neutrality in context