Mangling REX Loops with Propellerhead ReCycle

Use ReCycle to Mangle Your REX Format Loops Beyond All Recognition

by Craig Anderton

The REX file format, invented by Propellerhead Software, "slices" a rhythmic file into several pieces (e.g., every 16th note, although you're not restricted to particular rhythmic intervals), which are triggered for playback. This allows for easy time-stretching, but as we'll see, REX files provide lots of other creative possibilities.

REX FILE BASICS

The individual slices of a REX file are triggered by MIDI. Slowing down the tempo causes these triggers to occur further apart, thus creating a slower rhythm. Speeding up the tempo moves the triggers closer together, which makes the rhythm faster. Some programs require a MIDI file to trigger the slices, although these are rarer than programs that can extract timing data automatically from the REX file. The REX2 file format supports stereo; the original version supported only mono files.

Because little DSP is involved, with the right kind of percussive material there's virtually no sonic degradation (particularly with stretching to faster rather than slower tempos). REX files also track tempo changes automatically. There are limitations; sustained sounds don't lend themselves to the REX process, and  slowing down loops generally gives inferior results to speeding them up.

The only real tool for REX file creation is Propellerheads' ReCycle program. You bring in a WAV or AIF file, then create "slices" at each transient (Fig. 1). This is a semi-automated process, but generally requires some manual editing as well to optimize these slice points. Ideally, each slice should have a discrete sound: A kick drum, kick+snare combination sound, high-hat hit, etc.

Fig. 1: This screen shot from ReCycle shows how a drum loop has been "sliced" into different sections that isolate each sound. Each slice has been "colorized" to make it easier to differentiate them - the actual program uses color much more tastefully!

When you save the sliced REX file, it also bundles a MIDI file that triggers each slice. When you bring a REX file into a host program, either a MIDI track will be created automatically that contains the MIDI portion of the REX file, or you'll need to somehow drag or import the MIDI portion into a MIDI track.

Note that because the triggers use MIDI, editing the MIDI notes will alter how the slices are played back. This offers a lot of creative options - you can even copy MIDI notes to trigger several slices at the same time, remove MIDI notes to "thin out" a loop, and the like.

LET'S GET "WRONG"

Although REX files are great for time stretching, it's also possible to create "wrong" variations on a loop to end up with new, and sometimes very cool (or at least perverse), alternatives. Normally you do this by re-arranging the MIDI data in your host program that drives the ReCycle audio slices, but the following method uses an "all-digital audio" approach. The key is to export each slice as its own WAV or AIFF file, then rearrange the order of these slices in your host program. (Note: This assumes you've already used ReCycle to "slice" your file properly in the REX format; also note that the tempo you set in ReCycle is irrelevant, because slices are saved so their durations fit the original loop file's native tempo.)

The first step (Fig. 2) is to call up ReCycle's Process menu, and make sure that "Export as One Sample" is unchecked in the Process menu.

Fig. 2: Unchecking "Export as One Sample" exports each individual slice.

Next, select "Export" from the File menu (Fig. 3), navigate to the folder where you want to save each slice as a sample, choose the file format, then click on "Save."

Fig. 3: Make sure you create a folder where you can save all these slices so they all end up in one place.

You'll also need to choose the export settings (Fig. 4). Usually you'd check the option to create a MIDI file, but that's not necessary in this case, as we're working only with the audio itself.

Fig. 4: Choose the desired sample rate and bit depth for the slice files, then click on "OK."

Now all the files have been saved into the folder you specific in previously (Fig. 5). The exported slices include a number that represents the order in the original file. For example, "filename" 001 is the first slice, "filename" 002 the second slice, and so on.

Fig. 5: The individual exported slices.

Now open your host program, and drag the slices into a track (Fig. 6). This assumes that your host supports drag-and-drop, and most do; otherwise, you'll need to import the slices individually).

Fig 6: In this example, REX files slices are being dragged into Adobe Audition.

Now, let the games begin! Rearrange slices on the same track, or as shown here (Fig. 7), drag slices to a different track in whatever order you want. Repeat slices, overlap them, reverse them, whatever...you get the idea.

Fig, 7: The slices are shown re-arranged within two tracks.

Set a "snap to" grid in your host if you want the slices to line up rhythmically as you drag them in, and above all...have fun creating your totally new sounds. If you come up with something really great, consider saving it as a new loop you can use in other projects.

Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.