Wouldn't it be easier to just hum the Jeopardy song in your head as you first sit down in the volt?
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I may be wrong on this (haven't tested it), but I believe there are separate volume controls for navigation and radio, so you should be able to just turn the radio down to zero and the navigation voice will still play. Ta Da!
#1 Jeopardy Song -- The point is, if the Nav is on you also have either AM, FM, XM, or Bluetooth. The first 3 keep making noise and sometimes I don't want that. With Bluetooth, if it is set to music (iTunes collection) there is autoplay of a random song or a song I have selected. While I can manually pause either, anytime I change the volume on the Nav autoplay resumes where it left off. If a playlist had ended, it starts over when I touch the volume. For some reason with the YouTube video, I don't get this resumption of autoplay when I change the Nav volume. I find I change the Nav volume a number of times on a long trip as I want to hear clearly when approaching a complex, unfamiliar interchange while i want it down during stretches I'm familiar with but still want a reminder not to miss my exit. Also turn up Nav volume at highway speeds and lower it when I slow down.
#2 Separate volume controls for Nav and radio -- Yes these do exist but the radio volume resets to a default volume every time the Infotainment system is turned on and would need to be turned down each time the vehicle is restarted (several times on a long road trip for each bathroom break, meal break, and stops to purchase that nasty gasoline). I think I can change the default to a low volume but sometimes I actually do want to listen to something so then I'd be turning it up each time. All of these procedures are workable options but also are workarounds for a system that I would prefer to exist as 2 separate entities (entertainment and Nav). And, while I could just use the GPS on my phone, I do like the bigger screen that the Volt offers and the ability to hear the directions through the car speakers. So, I offer my "personal solution" here for those that didn't realize the YouTube videos aren't susceptible to the autoplay problem. Podcasts are also not susceptible to autoplay so if a podcast is completed, autoplay will not restart it with each touch of the volume button (but podcasts are auto-deleted from my phone 24 hours after listening so my weekday podcast isn't there during a trip on the weekend and autoplay again randomly selects a song from my music library if I haven't queued up my preferred YouTube video which I leave open in a Safari tab at all times for this purpose).