@alexparisella: Hello Alex,
To create a child theme you can use our plugin Generate Child Theme.
Install and Activate the plugin.
Then,
Go to => Dashboard => Generate Child Theme => Select Parent Theme as Zubin and fill in remaining fields and Click on Generate.
This will create and activate the child theme.
Then,
Copy the header.php file from the parent theme to the child theme folder.
Edit the header.php in your child theme, after Line no 26 add the following Code.
<audio autoplay>
<source src="http://localhost/wordpress/wp-content/uploads/2021/04/While_You_Work_It.mp3" type="audio/mpeg">
Your browser does not support the audio element.
</audio>
Finally replace the audio src file with your file.
Let me know if this works out!
Kind Regards,
Skandha