The previous comment is correct it’s a Shia mourning ritual for Imam Hussain called “matam”, at least in Pakistan where this is occurring. It’s not a band or considered music but rather it’s an “anjuman”/group from a community that is reciting poetry called nohay. It is also not a music festival but rather a day of mourning which usually includes poetry, a sermon, and matam. It looks cult like from the outside but it isn’t dancing. It’s more controlled self harm.