Jason Robards was the cemetery singer?

There's a funeral scene early on in Asssassins (from 1995 with Stallone and Antonio Banderas) and the man singing looks EXACTLY like Jason Robards...

But the movie's not on his page and I'm wondering if it was another uncredited cameo like Crimson Tide or Enemy of the State?

(I copied and pasted from a post I put on his board, so we'll see what happens.)