I need to start blogging earlier, too, but I guess you didn't completely steal my thunder, Clint.
The first time I watched Blue Velvet my initial reaction to the opening credits went something like, "All right. Blue curtain. Looks like it's breathing... SWEET FLUTE AND OBOE HARMONY!"
So I think it's pretty obvious that a film's soundtrack is extremely important to me. Kryzs said to "fondle the details," but I found it rather difficult to get intimate with camera angles and movement. We just weren't familiar enough with each other.
Instead, I made observations (no analysis yet) on every single musical transition throughout the movie although I admittedly got a bit lazy at the end and stopped documenting every single ominous lick.
1. The first time Jeffrey meets Sandy, the music starts creepy, begins to swell, and ends in a major chord (pretty much the first major tone in the musical score) as she steps out into the light. In fact, in the music composed especially for this movie (not "Blue Velvet" or "In Dreams"), the only time there are major tones is when Sandy is around. The next time there is a truly "comfortable" melody is the scene when Sandy is talking about her robin dream in which pipe organs (because they next to a church, which is probably another relevant observation) introduce the euphonious melody that plays again when a.) Jeffrey tells Sandy he likes her b.) when Jeffrey and Sandy are really into each other at the party c.) when Sandy instantly forgives Jeffrey on the phone d.) when the ending credits are rolling.
2. In contrast, when Sandy first shows Jeffrey Dorothy's apartment, the music ends in a resounding and discordant minor augmented chord (I think--my theory and ear training are a little rusty), which is very "uncomfortable."
3. A lonely little solo clarinet plays both times when Dorothy is standing in the bathroom, trying to cope with her situation.
4. This is opinion, but I thought the second time Dorothy sings "Blue Velvet," after she has met Jeffrey, there's less gloom in her voice, almost as if she has more hope.
5. I don't know if this is significant, but every time Jeffrey is driving somewhere a distinct hi-hat beat starts, with a jazzy bass line running through it.
6. And of course, let's not forget the little Lumberton radio jingle, especially since it starts directly in contrast with the unpleasant beetle scene.
There are other little things, but those are the most prominent ones besides the obvious ominous music playing when something bad or suspenseful is happening.
One thing I found that in Blue Velvet's soundtrack that I don't usually encounter in other films is that there is often a distinct incongruity between the music and what's showing on the screen. Normally, you can listen to the music playing during the scene and understand the scene's tone or feeling. I've found you can't really do that in Blue Velvet. An obvious example is when the Roy Orbison song is playing and Jeffrey's getting pummeled, but there's another example that bothers me much more.
When Jeffrey and Sandy first meet and they are walking down the street, the music seems much too eerie or mischievous. It doesn't match with what they are doing, conversing about a kid with a big tongue and chicken walking and generally just having light-hearted conversation. I noticed this the first time I watched it, and it still bothered me the second time through. Then again, lots of things about Blue Velvet still bothered me, so it's not really surprising.