Much to the misfortune of the nation and world, the current conservative establishment built its power on propaganda that overcomes any level of absurdity with aggressiveness. Bill O'Reilly, Rush Limbaugh and the Wall Street Journal editorial page are good examples. For example, they led the nation to war over WMD in Iraq, they deny climate change, they talk about death panels, Obama's citizenship, etc.
I don't see that elsewhere on the political spectrum. There are fringe left-wing outlets, but they aren't the top-rated cable news channel and leading newspaper.
Which doesn't mean it's part of a propaganda machine, it just is.
An example of this is horror movies. Suspenseful scenes will be suspenseful, even without any accompanying visuals. Even if you realize on an intellectual level that the music is engineered to make you feel stressed or nervous, it is exceedingly difficult to prevent yourself from feeling those things when you hear the music.
Or maybe that's all just me. I am very wary of the use of music because of this (primarily in situations where somebody else is subjecting me to the music; I'll listen to it voluntarily when I get to control what it is, but I try to avoid it as much as possible in any commercial setting).
The emergence of internet based video propaganda is particularly interesting to me, since it typically bypasses copyright law to use whichever music it pleases. Lots of popular pop songs being used in the background of blatant propaganda videos. Here is one rather extreme example (in terms of music use, not really content): https://www.youtube.com/watch?v=HRqw0VE5SUY My understanding is that the Russians made it.
Actually, it's sufficient just to not be liberal, and to a lesser extent, be neither liberal nor conservative. (But the liberal machine is much better oiled and more generally competent, moaning about Fox News notwithstanding.) It's hard to see propaganda that you currently agree with. (I do not exclude myself from that general statement, it's just that what I find harder to see is quite different than what the general US news is currently propagating.)
But I'd also observe that even standing outside the mainstream of US political propaganda, I'm not convinced there's necessarily a cabal of insiders sitting around in their smoke filled rooms figuring out how to "keep the masses in line". I think instead you've got people figuring out how to push their agendas, often in groups, and through a process of natural selection on the agendas in question you end up with agendas that tend to satisfy people to some extent and "keep them in line". You need not "conspire" to push fairly popular ideologies on people, you need only let the adherents of those ideologies do the things they naturally will do anyhow.
Edit: Look, downvoters, you might not like to hear it, but the US propaganda machine is liberal, or at least, Democratic (if you are more liberal than the Democrats and consider them "conservative"). Look at the political affiliations of the media, Hollywood, the bureaucratic apparatus, the University and academic system, and to believe that the propaganda system isn't Democratic is to believe that all of these things are peopled by 90%+ Democrats yet somehow transcend their political orientation to push... what, exactly? It's not even close... it's not like it's 60-40, it's 90%+ plus on every survey ever taken of those groups in recent times. Note my claim here is an objectively verifiable fact, not merely an abstract partisan snipe job. Ask yourself, what else would they be pushing?
If you don't see this, well... it's probably because you're not seeing the Democratic propaganda as propaganda, leaving you seeing only what gets through that isn't.
Further edit: Would someone care to post and explain the social mechanisms whereby the media et al is populated by Democrats yet is pushing some other form of propaganda on us all the time? Evidence would suggest it will get you highly upvoted. (Personally I'd suggest the fact that people just downvote but aren't posting suggests that this is either not possible, or very hard. This probably means something.)