Just something interesting I figured -The origin of qawwali was without any repetitive lines. Like the song would start and end real soon, in one shot. People weren't paying much for it. The wordings and feelings were beautiful but the artists weren't able to capitalize on this and they were living meagerly. One little newbie punk thought of a revolutionary idea and figured they could bore the audience a little bit and then excite them a little bit. Bold idea because audience can get real nasty sometimes. They tried it one day by saying something like "Artist needs encouragement for singing, so please shower them with $blessings$". It worked. The Artist would start singing and start repeating the same line without moving forward and some audience would go to the stage and shower them with $blessings$. And hence came the repetitions. Now its an art form, in the Indian/Pakistan royal gharaanas who still pursue such fading but unbelievably brilliant art forms of India. "Thoda abhi, thoda baadmein."
Another random etiquette if you ever go to a qawwali concert - don't ever "throw" money on the performers. They are very respected and there is no direct contact with them. Walk slowly towards them, smiling, with respect and leave the money near his feet. You can dance a little bit if you want. You can usually tell the novices from the gharaanawaalas by how respectful they are.