All of the songs on The Immaculate Collection (with the exception of the two new songs) were remixed by Shep Pettibone alongside either Goh Hotoda or Michael Hutchinson and some were also edited down from their original lengths in order to decrease the overall running time. While all the vocals remain the same as in the original recordings, "Like a Prayer" and "Express Yourself" feature different music backing Madonna's vocals than their original album release.

via en.wikipedia.org

So it turns out the Madonna songs on the "1989 A Novel" soundtrack are inauthentic, because I was using the Immaculate Collection versions, which are remixes. Question is, are they sufficiently different that I should feel obligated to purchase the original versions? #xrisworldproblems