>the frequency of the music made people have seizures and pass out
A variation of an 'infrasound' weapon may have been used at Astroworld:
September, 2019: "A new weapon invented by Chinese scientists uses low frequency sound waves to cause physical distress, forcing rioters, protesters, or anyone else the wielder wants to vacate the area. The Chinese scientists claim the weapon, developed by the Chinese Academy of Sciences’ Technical Institute of Physics and Chemistry, uses “focused waves of low frequency sound” to cause “extreme discomfort, with vibrations in the eardrums, eyeballs, stomach, liver, and brain”. The South China Morning Post, reporting on the weapon, says it has no moving parts. The Post further stated, “Professor Xie Xiujuan, lead scientist on the project, said the device was powered by a tube-shape vessel containing an inert gas. When heated, the gas particles vibrate and a deep, monotonous sound is emitted.” This sound is likely infrasound, a category of sounds lower than 20 hertz that are inaudible to humans. According to the U.S. National Institute of Health, infrasound’s effect on the human inner ear includes “vertigo, imbalance, intolerable sensations, incapacitation, disorientation, nausea, vomiting, and bowel spasm; and resonances in inner organs, such as the heart. [1]
September, 2019: "Hong Kong’s democracy protesters may be in for a nasty surprise in the coming months. The mainland Chinese have reportedly designed a sonic weapon that can selectively target individuals or groups in a crowd of demonstrators, leaving them unable to control muscle movement and render them easy pickings for riot police to round up." [2]
[1] https://www.popularmechanics.com/military/weapons/a29216045/chinese-sonic-weapon/
[2] https://jnlwp.defense.gov/Press-Room/In-The-News/Article/1983606/a-new-tool-in-chinas-kit-of-repression/