Was he inviting me to go with him?

Yeah it sounds like he might have been in a not very clear way.

But I understand why it would be awkward to jump on the half-offer. Dont do that. Say to him something like:

"you know I love that band too, if you can get me a ticket ill pay you back! Any of your other friends coming?"

Then it sounds neutral, more a friends kind of thing, especially as you suggested other friends coming. Its more relaxed, casual, which is what you want, especially if you like him. You want zero pressure.

And He'll probably reply no to that, and you give another cool low-key answer like "Thats cool, I dont mind either way, just us would be great too, sounds a great concert."

Or its up to you, if you did feel thats two big a step to go with him on your own, just say mind if I bring a friend. Maybe even you "planned" to bring a friend and she mysteriously "cancels" at the last minute ;) You use your instinct on how to play it.

But anyway whether you just want to stay friends or whether you might end up more than that, because its neutral its the perfect way to play it.

Have fun, good luck.

I don't know. I'm not sure if he invited you. I'm just as confused as you are. Ask him to go :D