Not "in Al Aqsa." Not "in the courtyards of Al Aqsa." No, their complaint is Jews singing somewhere in the Old City adjacent to one of the gates leading to the Temple Mount that Jews are not allowed to enter.
Jews don't visit the Temple Mount on Saturdays, but Palestinian and Arab media publishes stories about their "Talmudic rituals" and "provocative dances" every day even on days they do not ascend.
Which means that even if Jews were completely banned from their holiest spot, the Palestinians wouldn't be happy until the Jews are driven out of the wall of the Old City altogether.
Here's the video that is so upsetting to them. The Jews are singing "Shir Hamaalot" (Psalms 126) to the tune of "Hatikvah." Notice that the Arab shopkeeper right next to them nearby doesn't seem to be bothered at all.