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Liquidsoap has a very interesting feature named "Smart Cross" which overrides your crossfading settings. What this basically does is it check the two tracks (we'll call them A and B) and performs the following:
a) If A and B and not too loud and close (meaning the decibel levels are similar), fully cross-fade them.
b1) If B is significantly louder than A, only fade-out A. We don't want to fade almost silent things.
b2) If A is already very low, do not fade out.
b3) If A is significantly louder than B, only fade-in B.
c) Otherwise, A and B are just too loud to overlap nicely, or the difference between them is too large and overlapping would completely mask one of them.