We tend to think of fuses in an almost binary sense, ie the circuit is closed or open depending on fuse state.
But fuses are resistive devices designed to essentially "burn out" at the right time. Heat is generated to various extents at all times by design to accomplish that goal as a result of resistance designed into the fuse . I suppose its very possible the heat alters the composition and electrical conductivity characteristics of the fuse element prior to "blowing" in a manner that might effect the sound as a result in changes in electrical properties at some point perhaps compared to "new".
I'd be willing to bet that this is perhaps a reason why some hear a difference when replacing an old fuse with a new one, especially an "audiophile" type fuse where one is perhaps tuned in and listening for a difference by design when making the change. Better electrical contacts at the fuse holder as a result of the replacement operation is likely another at least as significant as anything else. Some report "Better sound" replacing a fuse with even a fresh conventional fuse compared to some fancy fuses.
It's all about as clear as mud but this makes as much sense to me as any other theory or reason why different fuses might sound different.
