I get the editing part, but one would think that a sound package applied would allow the default sound to be used if none is supplied. Just like IconPackager doesn't change the icons not contained in the package.
If this is not the case, maybe it's a feature that should be added.
It'll be a pain in the ass to us SP if I have to edit each package.
Sorry to hear you are having issues. Need to know what sound package you are using and which notification sound not played. So that I can test it out.
Stardock Community Assistant.
Using the Commander package by Stardock design.
Like the notification sound I used to get when I install a windowblind.