SQL inner join and on multiple rows

so, I am creating an music database. I am using three tables (files, categories, categories_assignments).

I want to be able to select a file that is in multiple categories (e.g. a song that is both pop and rock)

I already have made the or variance (included below for reference)

SELECT DISTINCT `files`.`filename` FROM `files`
INNER JOIN `categories_assignments` 
ON `files`.`id` = `categories_assignments`.`fileid`
INNER JOIN `categories` 
ON `categories_assignments`.`catid` = `categories`.`id`
WHERE `categories`.`name` = 'rock' OR `categories`.`name`='pop';