@shadowetheria Use a extention.
Click on the Opera menu icon (top-left corner) and select "Extensions" > "Get extensions" to open the Opera add-ons page.
Search for a Background Music Extension:
Use the search bar to look for extensions that allow you to play background music. Some popular choices are "Background Music," "SoundCloud Player," or other music player extensions.
Install the Extension:
Find an extension that suits your needs and click "Add to Opera." Follow the prompts to install the extension.

Configure the Extension:
After installation, you might need to configure the extension. Look for its icon in the Opera toolbar, click on it, and follow the instructions to set your preferred background music.