Why did he take a week to call?

Guys need time to think sometimes; and if he calls, he's interested, so go with it and see where it goes. And I like the 'relationships that warm up slow last'...it gives me hope, too.

he's in a relationship and had to figure it all out he needed time to work both ends, test it by saying i cant go to the concert but let's something else at a different time, let me know maybe i am wrong

So, you're wondering why he took a week to call, instead of calling the next day? He might have been busy. He probably has a job, so he could have been doing that. Or, like ethan1113 said, he could be in a relationship. I doubt the second one though. Just, a busy life.
And, if you're asking why he asked you back out at all, then maybe he likes you. He might like concerts, and maybe though you would like them too.
I would go. Have fun with him. If it doesn't work out, just tell him. If it does, then lucky you :)

Relax, miss. He called! No wonder men are always second guessing and buying books like "The Game" by N. S. Chill out and enjoy the concert.

Could be many things. I doubt if he is shy, because he DID call that night to be sure you did not give him the number for the rejection line! LOL. But could be because he was trying to think of something that might be a good first date. Could be he was playing that old guy thing where you don't want to look desperate by calling sooner than 3 days. Could be he's managing several gals...but you can determine that pretty quickly by how soon he asks you out after that first date (IF a second date is even a consideration). Almost too many potential reasons to know...but if it had been me, I would not have waited quite that long to call you. But he may have had good reasons...just coulda had a bad week at work/family issues, etc. I'd give him a chance to prove he's either genuinely interested...or just a "playa." That will become apparent right away. Keep him guessing and don't give up anything sexual. If he's genuinely interested and NOT a playa...he'll continue to pursue you. If all he wants is sex, he'll give up if he gets nothing after 3 dates. That's my $.02 worth, from the guy side of it.

Use your own observation, wisdom and patience.

Play it cool and dont look needy. If he really likes you, he will keep calling. Relationships that warm up slow last.

i wanna go to a concert! men don't call immediately. its just what they do. they wanna seem cool. every now & then you'll come across a guy who calls you the next day (6 messages? are we effin serious...WTF) but those guys are a lil scary. so yea. sounds like he's not a call just to chat kinda guy or he might have called sooner. he needs a date for his concert so he called you back & asked you out. he could have asked someone else.

well, maybe he had to make sure of his move...or maybe, he wasnt sure if he's gonna pursue you or not...or...he tried to evaluate his feelings for you..whether a mere attraction or love..

You have to be patient some times havent you heard of wating to call distance makes the heart grow fonder hopefully hell be worth the wate but theres no need to rush

Thats what everyone does.... How many time have you got a guys number and waited to call him?

It like this unspoked thing wait to call... Silly isn't it