It's being billed as a special appearance -- even amid a busy slate of local events for the president -- because the first lady will be joining him.

And now -- it seems -- so will Alicia Keys.

An updated copy of the invitation was just sent out by Suffolk County legislator -- and prominent Long Island fundraiser -- Jon Cooper announcing that Keys will be a featured performer at the gala dinner.

Tickets start at $2,500, and $100,000 will get you on the host committee.

Keys was in attendance, but didn't perform, at a star-studded fundraiser for the president a few weeks ago at Harvey Weinstein's house.