Most Helpful Guy
I'd play it off like you're expecting that it's NOT an invite, and just make it part of confirming your itinerary. Just be like "yeah, so we'll be there on Friday . But you have that concert, right? Do you want to meet up later that day or should I catch you the next day...", etc.
His response will either be "yeah, just meet up with me (whenever)...", or he'll be like "wait, are you coming to the concert with me?"
I'd probably assume he's going to the concert alone/with friends though, since it's probably something you'd buy tickets for in advance, and he didn't specifically ask.
Most Helpful Girl
Be prepared to go but also be prepared not to go. This way it isn't awkward asking.