This is a very simple mod / sound replacer. It takes some of the generic "Hello" and "Hail" greetings from vanilla Oblivion and copies them into the locations for some of the generic NPC greetings which are not voiced in Morroblivion. If you want to put more generic "Hello" greetings in place of silent NPCs, I recommend using the Construction Set Extender instead of the original CS to help you "import" an Oblivion greeting into the appropriate file location. The extensions in the CSE are extremely convenient for working with dialog. I remember there being a tutorial for using the CSE's extra features to import dialog, but can't seem to find it now. If anyone knows, please post. Thanks.
Of course, ideally, the best way to implement these generic greetings isn't by brute-force copying the "Hello"s and "Hail"s into every generic greeting file location, but by modifying Ely's Universal Silent Voice to dynamically detect a missing dialog greeting and to choose an appropriate generic greeting from Oblivion that matches the NPCs race and maybe also their disposition level -- that way, you don't get a happy sounding "Hi!" when the NPC is frowning. Unfortunately, the source code for Ely's Universal Silent Voice isn't available, and I don't have the time right now to figure out how to re-write it from scratch. Any volunteers?