Ay Iran is the unofficial national anthem of Iran. The Shah had his own (praising him, of course) and the Islamic Republic has another. However, Iranians everywhere learn and sing this song as a symbol of their pride and identity outside whatever opressive regime happens to control them at the time. The best analogue for us would be America the Beautiful - but imagine a Sarah Palin led coup had replaced The Star Spangled Banner with some song praising the coming rapture.
I will never forget how moving it was when a wedding I went to in Tehran broke out singing Ay Iran. It was a simple act, but to me, the outsider, it seemed like an extremely meaningful, though simple, act of political defiance.
I hear the protesters are in the streets singing it tonight, and my thoughts are with them.
Ay Iran.