Yes, I am aware of the answers listed here: How do I fade music in and out using Blender?
But neither of them seem to work for me? I cannot get a keyframe to be inserted on just a single channel (the I key seems to do nothing) and when I use the "insert keyframe" button it gives me an error asking for the type of keyframe, something not addressed in the original answers. Furthermore, when playing around with the type of keyframe I am able to get it to be inserted for all channels (maybe?) but there is no color change as indicated in the original answer, nor does it actually allow me to change the volume independently across the keyframe boundary.
The second answer seems to require me to have two complete audio tracks for the same song going at the same time and crossfading between them as I want the music to go down during narration. That seems inelegant and inefficient and I am also not sure how that actually controls whether the music is fading in or out.
So I come back to the original question: How do you actually fade music in and out? If keyframes are the answer, what sort of keyframe is required on the channel and how do you just insert a keyframe directly to a single channel that the system will recognize?
Right now it seems like I need to make a cut every other frame or so and manually step the volume down or up for each clip...and that certainly can't be correct, can it?