Unfortunately, fair use is a "I know it when I see it" deal, decided on a case by case basis, so there is no definitive answer.
There are four factors of fair use:
1)The purpose and character of your work: Arguably, you work is both transformative and educational. This seems to be in your favor.
2)The nature of the copyrighted work: Factual works are more amenable to fair use than creative works: thus this point is against you.
3)The amount and substantiality of the portion taken: Provided you don't use too much of either source, you should be alright here. Note that total length or proportion is not necessarily key: there is a court case where quoting a few key paragraphs out of a biography of hundreds of pages was found to be infringing as they were "the heart of the work". If possible, (and seemingly ironically) using multiple pairs of music albums/songs and movies might be better for you, in terms of fair use.
4)The effect of the use on the potential market of the work: This is mostly about the ability of consumers to replace the original(s) with your product; I don't think you have too much to worry about here.
As a final summery: You should be alright, so long as its a commentary, rather than a project. Actually creating and displaying movie synchronization is probably not fair use; creating a commentary on the phenomenon is probably fair use. (E.g. mentioning that you can have interesting effects synching up, say, the Lord of the Rings movies with say, Abbey Road is fine. Actually displaying more than a small snippet of the result is probably not). Using smaller bits of multiple sources will help you.
As a final warning: fair use, even if correct, can be hard and expensive to prove. I would bow to any take-down requests you receive, but IANAL.