Last November Adam Thirlwell wrote a brilliant review of Twin Peaks: The Return for the New York Review of Books. I'm going to have to reread it to digest Thirlwell's references, but one I noticed as I researched his review is that the song "My Prayer" by the Platters, which appears twice in the series--in Parts 8 and 18--reflects the recurring Doppelganger theme in the series.
One of the singers on the Platters was named "David Lynch." David Lynch of the Platters died in 1981. In other words, the double use of "My Prayer" involves a reference to Lynch's own Doppelganger, just as Cooper has a Doppelganger and Cooper's Doppelganger has one.