Edit: I see you’ve answered your own question, but the answer you provided seems dubious to me, so I’m going to post this anyway.
A child theme needs a few key elements to work: a style.css with header information (including Template: parent-theme-name), a functions.php file (where you can enqueue the parent theme’s stylesheet), and activation of the child theme from the WordPress admin. Learn more about child themes in the WordPress Codex.
Once you have your child theme activated, all files in the child theme will override templates in the parent theme with the same name. Take a look at the template hierarchy to better understand the names of these templates and how they take precedence.
Finally, let’s talk about page templates. You have the right idea by calling the file concert.php since for custom page templates, the file name should not be prepended with page-. This is used for specific slug- or id-driven page templates. At the top of this file, you need to include /* Template Name: Name of Template */, just like you have already. This will appear in the page attributes under Template. After creating this file and storing it in the child theme, you must select this template from the drop-down list under page attributes for your new page. More information on page templates in the WordPress Codex.
I hope this helps!