If you start playing MW3, you can hit 'A' on a second controller to play with you split screen on live.
Also, you can hit 'Y' and invite friends, making a party through some games.
Are you able to do these two things together?
Moreso, I may want to do private party chat through Live versus in the game.
When starting the game back up, after joining in a party, the option to hit A was not there.
Is there a way to be in an xbox live party and have a guest join in on the game?