When we were young Muharram observation was not just for Shias. Some Sunnis (e.g. wahabis) did not approve and there was some sectarian tension in places, but the current murderous anti-shia campaign had not yet started (General Zia helped set that in motion, like many other things). Centuries of prominent Shia presence in Indian Islam had created a powerful penumbra of karbala symbolism and Hussainiat among the Sunnis. So PTV went all black for ten days in Moharram, with daily programs about Karbala that reached their climax on the tenth of Moharram. That night the observance included a telecast of the majlis sham e ghariban (commemoration of the “night of the helpless”) followed by Nasir Jahan reciting the salam e akhir (final Salam). I dont know how many Sunnis watched it but we almost always did. Hussain and Karbala had become standard symbols of revolt against tyranny, so left wingers felt a certain kinship with the whole thing even if they were not Shia.
Now, matters are rather different. PTV is no longer the only channel, so the common idiot-box experience that all middle class Pakistanis shared is in any case no more. But beyond that, two decades of relentless anti–shia propaganda by the sipah e sahaba and their Gulf patrons has done its job. For an excellent account of modern shia life in Pakistan, read this piece by young lawyer Feisal Naqvi. I havent had time, but if someone has links to other shia perspectives about everyday life in Pakistan, do post links in the comments.
Meanwhile, here is the incomparable Nasir Jahan.
And a majlis from the late allama naseer ul ijtihadi