From Wired How-To Wiki
So you want to take a stab at making a remix? While Greg Gillis didn't just pick up his laptop and become Girl Talk—there is a methodology to the process. But it involves steps that anyone can learn in order to create custom mash-ups and enhanced tracks. Here’s a breakdown of what you’ll need to consider, by DJ Mr. F AKA Ross from Tally Hall.
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What you’ll need
This may seem pretty straightforward, but there’s a lot to consider here. At the very least, you’ll need to get your hands on the vocal stem, or vocal tracks from the original song. You may want more; perhaps you want the remix to also include the original guitar or keyboard lines, in which case you’ll want those stems as well.
You can get stems a variety of ways, but depending on what you want it may require some hunting. One option is to contact the label or the band directly to acquire them. Otherwise, you may want to scour the internet to find them. And if all else fails, it's usually pretty easy to find acapellas online. (Note: You'll only have the vocals in that case, but don't let that discourage you. This method tends to lead to the most creative remixes.)
You’ll also need audio sources of your own to add to what you use of the original mix. This can be anything from individual drum note samples (snare hits, clap samples from a Roland 808), to full-on bass line loops, drum loops, or better yet, your own instruments (assuming you have the means to record them properly).
You can make samples yourself, recording acoustically and modifying the sounds to achieve exactly what you want to hear. However most music programs will come with banks of them. Logic and Reason for example will come loaded with thousands of samples to choose from. And if you're up for a little searching in the area of hazy legality, you can often find downloads for them online by searching for keywords like "Samples", "Drum kits", "production kits" etc. A good place to start your search is www.hiphopisread.com.
You’ll want a good audio editing and mixing program. I use Apple’s Logic, and swear by it. However ProTools, Ableton, Cubase, and Reason are also very popular and will do the trick. I prefer Logic because it’s a great middle ground for digital production and live audio recording. ProTools is still the industry standard for use with large studios and multi-track recording consoles; Ableton seems to be a favorite for those who work entirely within their computers (no real audio capturing). Logic offers the best of both worlds, and if you’re a Mac user already, it will seem incredibly intuitive.
The best and most comprehensive programs are not free and certainly not cheap. But you may be able to find demo versions that will allow you to try the programs out before making a big investment. Many of the digital interfaces come with a free version of Protools LE or a similar "light" version of recording software.
Before you jump in and start toiling away, think about what you want to accomplish. What does the original song sound like, and how do you want your remix to compare to that? In general, most people would answer that with, “It needs to be dancier.” This is fine, but not all remixes need to be dance remixes, and even if that’s what you decide, there are many dance styles. Perhaps you want to go the more modern route, using mostly synthesizers, or maybe you want to shoot for a Motown feel, adding some horns and background vocals to the mix.
Create your session
Now it’s time to get mixing. You’ll want to begin by adding the vocal stem (as well as any other original stems as you decide) into your program. Each one should be its own track. It’s important that you learn the proper techniques for using whichever program you choose.
Set your tempo
Since much of the audio you’ll use will be snapped to a grid of measures and beats, or full loops, if the tempo set in your program does not line up with the original audio, things will go awry fairly quickly. Some programs such as Ableton will detect the tempo for you automatically, however programs often have difficulty doing this when there is no apparent beat. This is usually the case when you're dealing with stems that do not include a drum track.
My advice is to use the original song to detect the beat, or to use your eyes and ears to sync it up (you'll be able to clearly see the beat by looking at the drum hits versus your program's grid, and you'll also be able to hear how in-sync the drum hits are with the metronome in your program). When all else fails, if you're very close, but it seems to get off every phrase, verse, or just somewhere in the middle of the song, you can always cut up the tracks into smaller pieces, working one or two measures at a time, and nudge them until they sync into the beat.
Pro tip: Trust your ears! Nothing will give you better results than listening to the flow of the original track and making sure that the stems or vocal tracks line up with your remix tracks in a similar fashion.
Adding your beat
Once you’ve determined what you’ll be using of the original track, it’s time to begin adding your own audio to the mix. I prefer to start with drums. It’s common to find drum loops and simply add those in, however there is a lot more creativity to be found by getting your hands on individual samples and placing them where you’d like in order to create a beat from scratch. Within Logic, there are thousands of Apple Loops, which are a great tool, and can be easily placed right into your track without even having to look outside of the program. Just keep in mind that if everyone only used Apple Loops, we’d start hearing a lot of the same sounds on every remix out there. While some of the best hits of the decade have relied on these (Rihanna’s Umbrella uses Apple Loops’ “Vintage Funk Kit 03”), I’d sure get sick of it if I heard it on 25 other songs and remixes all the time.
So be creative — use standard loops some of the time, or to help foster ideas, but try to avoid using stock loops for every part. However you choose, making a solid foundation of the beat will help to guide the rest of the parts as you move forward.
Adding your bass
Generally you’ll want to move onto the bass line next. This can be achieved through software instruments (most of these programs have great built-in synthesizers and a bank of solid bass tones to choose from). Again, the stock tones may be awesome, but it will pay off to tweak them a little. Make sure it’s just the right sound that you want to hear in your remix. From there, it’s merely a matter of hooking up a simple midi controller, and playing in the parts. Logic even allows you to use your qwerty keyboard to specify notes if you’re feeling especially thrifty. Though, if you have the means to get your hands on a real analog synthesizer, or you can convince your bass player friend to come in and play some funky licks for you on his old Rickenbacker 4000, more power to ya.
Once you’ve got your drums and bass, you can start exploring a little more. Consider adding more auxiliary percussion, synth pads, string, arpeggios, you name it. And as you discover new sounds that you want to add, keep in mind the overall structure. Maybe the drums should cut out for a section, or the bass line should change up between the verses and the choruses. The more variety and creativity you use, the more alive your remix will become.
Perhaps you don’t really like how short the original version of a song is? Or how long it is for that matter. In the words of Professor Farnsworth, “Good news everyone!” It’s your remix. Feel free to chop the song up however you want to, add a few choruses to the end, or even a long noodling synth solo in the middle if it so moves you.
The last and often toughest part is achieving your final mix, for which you should research and understand the basic concepts of mixing. Learn how to use equalizing, compression, limiters, delay, reverb, and how to create sub-mixes before you jump and start moving faders around. The basic idea however is that you’re trying to create a space for every part of your remix. Its important that each instrument or track have somewhere it can sit in the mix where it’s not competing with everything else to be heard. And as a general rule of thumb, if you can’t hear something as well as you’d like, turn everything else down a little before you start turning things up.
Here's a sample I made with Ryan Brady to give you a taste of what you can do: