Post-templates?

Hi there,

I have made different sidebars for a few of my categories, it’s my way of making theme-pages about different music festivals i write about:
https://www.morgenutgaven.com/category/musikk/festivaler/hove/
https://www.morgenutgaven.com/category/musikk/festivaler/quart/
https://www.morgenutgaven.com/category/musikk/festivaler/oya/

So my question is; is there any way to make the posts inside a category with the theme-sidebar? So if you click on a post that belongs to one of these categories i would love the visitors to still see the themed sidebar.

Am I making myself clear in any way?