You can't add audio files to google slides presentations, but you can add videos.
49+ How Do You Add Music To Google Slides
Pictures. Open a google slides presentation in your web browser and go the slide to which you want to add music. Select insert > text box from the menu, or click the text box button in the toolbar.
How To Insert Audio In Google Slides Step By Step Shake Up Learning from shakeuplearning.com
You may have thought that adding music to your google slides is as simple as choosing the music and playing it during the presentation. Open a google slides presentation in your web browser and go the slide you want to add music. Navigate to insert > video.
Youtube works well with google slides, as part of the same product family.
Adding music to a google slide presentation can spice it up and keep your audience engaged. You can't add audio files to google slides presentations, but you can add videos. Click on a track that you want to add and click select button to add the audio to your google slides presentation. This can work even if you don't need the video to play.