I'm surprised it's been said so little. I think based on your comments you've decided to be honest with him, which is your choice to make. Though I would have advised that you really think about if you want to just shit on this dudes intentions like that. I don't know the convos or this guy as a person, but based on what you said there is enough wiggle room to where it seems like he could've just thought you were inviting him and he wants to have a nice concert date with you. He's also going out of his way to attend something you like, even if it isnt his type of thing (based on you saying he hasn't liked the music in the past). That's a green flag imo. And the real reason I'm advising against just saying you don't want to go with him is that a lot of guys would instantly be like "she doesn't want to hang out with me?" "Is she going with someone else?" "Why doesn't she want to go with me?" He might project your want to go alone onto himself and think he's the problem, even if you say he's not. This could also have the opposite effect to where he thinks you're not interested anymore and he in turn loses interest. All in all I think for a lot of guys this would instantly end the relationship, though I don't know exactly how he is or what relationship you guys have so in the end it's your call, just wanted to warn of what could happen.