badmartialarts wrote:Scintilla used to be into mash-ups, he might be able to offer more advice as to actual techniques used, but the basics are taking two songs with similar rhythms and adjusting their speeds using an audio editor like Audition or Pro Tools so that they sync, then cutting back and forth between them in interesting ways. It's not unlike making an AMV, except totally in the audio realm.
To me, the chord progressions are more important to match up than the rhythms, because it's a lot easier to change rhythms.
If you've got two songs that are similar in that regard but one doesn't QUITE match the other, sometimes you can make it better by rolling off the bass of one (high-pass filter) so that you only hear one bass line instead of two conflicting ones.
Example: "My Summer Love" in the chorus goes I-I-IV-V, while "I Saw the Sign" goes I-vi-IV-V; but the root of I is present in the vi chord (it's the third), so I high-passed "My Summer Love" and it fit.
Or, "Open the Door" (Magnapop) has I-V-ii-IV in the verse, while "Good" (Better Than Ezra) has I-V-vi-IV; the root of vi is present in ii (it's the fifth), so I high-passed "Good".
You also want to pay attention to the other parts of the frequency spectrum as well; there are times when you'll want to high-pass one of the songs just because the bass is way too loud and thumping otherwise, even if they match up; or you'll want to low-pass one of them because the cymbals are way too loud otherwise; or any number of other problems.
Of course, all this is MUCH MUCH easier if you can find an a cappella track of one of the songs, or a karaoke track of the other, or both. This was happily the case for my two most recent projects.
A mostly-complete collection of my bootlegs can be found here:
http://www.aquilinestudios.org/mixes.html
Though I never finished this one, it contains the "Open the Door" vs. "Good" dynamic I mentioned earlier:
http://www.aquilinestudios.org/openthed ... mplete.mp3
(For some reason, the QuickTime plugin for my browser is screwing it up; just save it to disc.)