Thousands of fans were taken by surprise when tickets for Hosny's first-ever Saudi concert in the western city of Jeddah on March 30 came with the edict that dancing was "strictly prohibited".
"Ladies and gentlemen, please fasten your seat belts," one Twitter user said.
"The corridors and seats will be equipped with sway detectors. Anyone who thinks about swaying will be kicked out."
Another tweeted: "No dancing or swaying in a concert! It's like putting ice under the sun and asking it not to melt."
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With its new modernisation drive, the ultra-conservative kingdom has hosted a series of concerts in recent months by artists such as Lebanon's Hiba Tawaji and legendary Greek composer Yanni.
Men and women are often seen breaking into dance at such events, in scenes that were unimaginable not long ago.
Crown Prince Mohammed bin Salman, who is leading the reform drive, is seeking to balance unpopular subsidy cuts in an era of low oil prices with more entertainment options -- despite opposition from Muslim religious hardliners.
Saudis currently splurge billions of dollars annually to see movie shows and visit amusement parks in neighbouring tourist hubs like Dubai.