trying to play X-Men Children Of The Atom but there is no intro music. The audio of the game it's self works just fine, but during the attract mode when you start the game, it's just silent. Not a big deal, I just thought that there could be something I could do. I tried the game on my computer and the intro audio is there. Don't know why it's not there on the nes classic.
A little late to answer, but by default the attract music is off in X-Men COTA. You need to go into the in-game Test Menu and go to Configuration > System > Demo Sound and flip it to 'on'.