Well, you need to store your settings at some point, and an ini file is the most obvious way for that. By doing that you automatically allow users to edit that file for configuring it
As a next step you could make a window for configuring it in-game. That has the added advantage that you don't have to worry about windows now.
At that time, it is also more clear which sounds you can actually change. That makes it easier to judge whether making a window for it is beneficial.
A good way to find things is either by reading the generated documentation (which is not complete), or to search through the source files for some keyword (for example a case-insensitive search on 'hot' gives me 52 source files). By reading the matched lines, you can get a good idea of which file is interesting. Otherwise just browse/read them all
In time, you will understand which files are used for what.
Oh, and a third way is to read the filenames, "hotkeys.h" and "hotkeys.cpp" seems like what you may need