First off, a fantastic mod! I was very disappointed when I got to space and discovered that LabDansen didn't affect Space Exploration's labs, so to see that injustice solved is satisfying.
However, one minor issue is that by default, all sounds in Factorio actually are affected by the Doppler effect. It's a neat bit of realism, but for this kind of sound (music) it's a little too strong. Luckily it can be disabled (and in fact it is disabled for things like the substation's working sound).
The relevant property is on the WorkingSound of the lab: use_doppler_shift: https://lua-api.factorio.com/latest/types/WorkingSound.html#use_doppler_shift
I will admit that it is kinda funny though, so if you don't want to completely remove it, you could make it a startup setting.

+1 to this. Also not sure if it's possible to prevent multiple tracks from playing at once when you open it?

I can look into the doppler effect as a setting.

I did set a limit to exactly one instance of the track playing at once, I assume you're referring to it switching when you walk past multiple labs? I'm afraid that's not preventable - or at least I don't know how. It makes sense that the core engine does not want multiple entities to play their sounds in sync usually.

I finally found the time to add the doppler effect setting. Still no luck with the synchronization though.

Any chance of making the doppler setting not a "game start" setting? :)

No, sound settings are prototype data and therefore need to be set at game start.

this would need a rewrite of the mod but you could rewrite it so that the sound plays when you are in range of any lab (adjust volume for how far the lab is) so that the sound is only played once and not by every lab (which causes the weird sound issues when walking around the labs)