I'm no expert, but I've read somewhere that the pause doesn't happen if you use MAFW to play the sound. This is the framework that the Nokia-supplied Media Player uses, which as you will have noticed, doesn't have that problem when you press the power button. There are also often stutters with non-MAFW apps (like Panucci, as you mention) when you use the right-hand side lock slider and when you rotate the device, by the way.