Hmmm, that's an interesting option.
When I use that, it eliminates the "gap" almost completely, unlike all the other things I tried.
But sadly it's not viable, because having the window focused or not at launch can affect this time calculation and end up looping at the wrong part of the song when you do click it to focus. (I think framerate my screw things up too, but I'm not sure).
I'm really starting to wonder if Construct 3 is going to have to implement it's own loop system that's better designed for this kind of thing.
I suspect Construct is adding the little "gap" at the beginning of my songs after rencoding, and I still have no idea how to make my own webm files that do not need re-encoding.