A mysterious third voice has randomly appeared inside NotebookLM

Summary

NotebookLM is Google’s AI research assistant, and it has an audio discussion tool called Audio Overviews that generates two voices.
Recently, a third voice has appeared out of nowhere in NotebookLM, according to Reddit users.
The spooky third voice could be a glitch, or a sign of things to come.

There are many different AI tools available, but Google’s NotebookLM is easily one of the coolest. If you’ve never used it before or are unfamiliar with it, it’s an AI research assistant that can summarize and make connections between different sources you upload, such as PDFs, websites, and YouTube videos.

One of NotebookLM’s standout features is its Audio Overview functionality. Essentially, this takes your sources and transforms them into a podcast-like audio summary, where two narrators engage in a “deep dive” discussion of them.

However, some users have recently reported an odd anomaly with NotebookLM’s Audio Overview feature, where they hear a strange third voice that seems to come out of nowhere. Some users believe it’s just a glitch, but it could be a sign of what’s to come.

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A third voice from beyond

Is this a glitch or a feature?

Typically, when you generate an Audio Overview, you hear a male voice and a female voice discussing your sources, so the sudden addition of a third male voice is alarming.

It’s unclear what’s causing this third voice to appear, but one Reddit user experienced it during an Audio Overview that exceeded two hours in length. Another Redditor noted they only noticed the third voice while creating long-form podcasts. One described the third voice as merely a “glitch” and remarked that they’ve observed “more glitchy voices lately.”

In another Reddit thread inquiring about when NotebookLM will add new voices, one user stated they thought it had already happened, saying, “I can tell they’ve added new voices because they pop up in my episodes. Very disconcerting to suddenly have a third host. He sounds young and has a casual attitude.”

So, is this third voice just a glitch? Or is it a feature currently being tested? In a recent AMA session, NotebookLM mentioned it was working on adding new voices and dialects to Audio Overviews soon (via XDA), but there’s been no news on an official launch yet. It’s possible the third voice users are suddenly hearing is a test version of the new voices Google is developing, but that’s just speculation.

Personally, I hope Google adds more voice options to NotebookLM soon. Its Audio Overview feature is one of the best out there, but if you use it frequently, hearing the same two voices all the time becomes extremely repetitive. Hopefully, this spooky third voice appearing for some users signals what’s to come, and not just a glitch. But right now, this feels like an episode of The Twilight Zone, but for NotebookLM.