While many users simply use slides as a background for their own real time speech, MANY of us would like to create slide presentations with background music and/or offline narration. "And/or" means loading the music and voice on separate tracks. Along with adding MUSIC (it's a greatly anticpated feature - trust me) would be the ability to change slides on command, not an "in every" choice, such as change slides every 10 seconds or every 3 seconds. As said better in another post, set showing time for each slide independently. Repeat: These are greatly anticipated features.
Basil Roderick commented
A huge change I hope it works
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Sean Chamberlin commented
As a workaround, Slides does let you export to Powerpoint, where you can narrate and record a presentation. Powerpoint now automatically includes closed captions in real time and that gets recorded so that can be useful to educators. As well, I successfully recorded a presentation using Zoom and sharing my screen of slides. So there are options available that can be useful to educators and webinar creators as well.
Voice over would be an awesome feature especially for educators.