As said above - depends on the music. Take the lyrics away from most of Johnny Cash's or Henson Cargill's songs, for example, and you'll end up with a big empty nothing. Not even tunes worth humming to really.
Quick work-around: If you want to have them use the same fuel load as you for their first stint, then set the number of laps for the race to as many as the amount of fuel you want to use permits then when the race starts, pause the game and set the laps to a bigger number with the /laps command.
If I remember correctly from when I was tinkering with some DirectSound stuff, there are flags you can set to the buffer that control the way it acts when the app loses focus.
But to be honest I can't recall many games that do that - atleast ones that didn't prove to be annoying in the long run. Perhaps as an option when someone has LFS windowed and thus could probably be watching a race while doing something else it might be useful.
I'd look for a custom directsound dll (dsound.dll) that has sticky focus (or somehow like that it's called) enabled for the buffer and then put it in the LFS directory, much like you'd do with the d3d hijacking mods out there.
I am under the impression that mozilla's offering works either way. At least I seem to remember some sort of rudimentary synchronizing some versions back that I checked it just for kicks.
It's exactly like analysing a lap - you can keep a training log with it. Charts of cardio/speed/cadence/watts/Kcal burned vs elevation, etc. High tech gadgetry for a sportier life. Check out Polar's site, they got demos that will generate more "?" marks over your head than you can imagine.
To be honest I too can't see what all the fuss is about - if it's expensive and no one buys it, they'll either revise policy or make it more tempting... somehow...