I have no real intent on participating more in this, but I feel I should share this…
I agree with reosarevok mostly. But I do want to point out that there do exist digital files that are “promo only”. I have some that actually have proprietary atoms and/or frames in the meta that indicate it is promo only. I do not intend to say what that means here, what it should mean or anything. I just wanted to add that digital promos (like CDs) do exist… but are quite rare in my experience compared to promo CDs.
The files to not have embedded DRM, you could simply delete (or add) such tags at will, etc. The audio portion of the file is the same as the retail, it just has a completely different meta… promo only indication, record company ownership, where/how to acquire licensing, etc. If I were not how I am and keep the metadata intact as received, no one would ever know my files are not retail files. With the metadata intact, a system designed to read such things will tell the operator the file is promo only.