This is an extract from The Editing Chef.

While it can always be done manually, Audition’s remix feature uses powerful AI to shorten or lengthen virtually any piece of instrumental* music. Because it can save a lot of work, or whenever you are stuck trying manually (or simply arrhythmic), it’s often worth a try. Often it does things you could never come up with on your own. Here’s how to use it.

*You can always try using it on music that contains singing, but don’t expect much. Lyrics can’t simply be broken, unless they’re as deep as a puddle.

Open Audition. Open the "Multitrack" instead of "Waveform" view. Call it what you want (no shame in it being "Untitled session 176" because you probably won’t need it again).

Now import your song and drag it into the editor. Right-click and go to "Remix" → "Enable Remix". Your song will be analyzed by the AI, which will take a second. Once that is done, a new icon will appear at the upper corners of your clip.

Put your mouse there and drag it to the desired length, and Audition will quickly shorten or lengthen it.

It’s very likely that you will be impressed by this powerful feature and wonder how Audition figured out such clever transitions that work seamlessly. If you’re not so lucky however, you will hear a transition that simply doesn’t work. Don’t give up just yet! The remix tab is there to help. It will open automatically in the properties window when you press on your clip.

You have several ways of adjusting the remix:

"Stretch to exact duration" does exactly what it says. By default, Audition will give itself a five-second tolerance to whatever time you have selected (you can choose between 5 and 30 seconds with the "Maximum Slack" slider). So if you want your song to be 30 seconds long, it might end up being 25 or 35 seconds long. By selecting this, it will stretch it to exactly 30 seconds, but this means messing with the speed which you usually don’t want. The other features can also affect length, so ignore this one for now (or better: Forever. Seriously, don’t speed up or slow down music unless it’s so mild one wouldn’t notice).

"Edit Length" doesn’t really edit the length of your clip as much as it affects its edit points. Going from 0 to 100 or vice versa can have a significant impact. The lower the number ("Short"), the more segments of the original piece will be combined in the remix. It is easier to explain with a video, so here is an example of a track with a "short" and a "long" remix.

"Features" gets a little technical. You can decide how timbre or harmonic the remix will be. This is not the right place for a musical lesson, but it will be handy for you to know that "timbre" works best for monotone beats, while "harmonic" will work best for more complex pieces with more instruments and different segments.

"Minimum loop" lets you decide how short a loop can be; this is especially relevant to when you make your clip longer, and it can have a significant impact on the end result. Just experiment with it until it sounds good to you.

Side note: Hover over one of the sliders or parameters with your mouse to reveal a description of what it does.

Now you should have a pretty good idea of how the Remix feature works. The only missing piece of the puzzle is to try it out for yourself!

Pro tip: Audition Remix usually works just as well for complex pieces, but don’t mess with famous classical music too much. The same goes for popular music in general. Not just to respect the art, but because everyone knows those pieces and cannot be fooled when it’s missing parts.