Loop-a-palooza!

Jun 1, 2002 12:00 PM, By Todd Souvignier

Wondering which loop-based audio software is the best for you? We've put Sonic Foundry Acid, Image-Line Software Fruity loops, Propellerhead ReCycle, Cakewalk Sonar, Plasma, BitHeadz Phrazer, and Ableton Live to the test.

Descended from the MIDI sequencer and the digital audio sequencer, multitrack loop sequencers represent a third generation in the evolution of sequencing software. By making it possible to easily tempo-match and layer audio loops, loop sequencers have already changed the way thousands of artists make music. Although the programs covered in this roundup are often surprisingly powerful and versatile, they all center on the lowly loop.

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LOOPOLOGY

For the purposes of this article, I'll define a loop as an audio file or a section of an audio file that is designed to play repeatedly. Loops are often short recordings of rhythm parts and are used as “building blocks” within larger arrangements. When a loop is edited correctly, it produces a smooth, continuous pattern. If the editing is sloppy, you'll hear a pause, an increase in speed, a hiccup, or some other anomaly.

When people first started working with samplers and digital audio sequencers, they naturally tried to layer different audio loops. That often proved to be problematic. If two loops aren't the exact same tempo and the exact same length (or an even multiple or fraction thereof), they just won't lock. The loops must match, and match well, or they will quickly drift apart.

SLICE AND DICE

The programs in this roundup solve the loop-matching problem by viewing each audio file as a series of individual notes, drum hits, or segments typically referred to as slices. First popularized by Propellerhead ReCycle and Sonic Foundry Acid, loop slicing lets you change the tempo and duration of a loop while retaining the original sound and pitch of the music.

Slicing doesn't really alter the sounds of the instruments. It just chops each loop into a series of notes and plays the notes at the designated time. When you slice up an audio file, you create an edit list or playlist that is tied to the composition's tempo.

That's a better approach than using digital-signal-processing (DSP) time-stretching algorithms to expand or contract loops. Aside from their other limitations, time-stretching algorithms almost always color the sound and frequently yield unnatural results. In addition, they demand considerable processing power.

When you import an audio file into a loop sequencer, the program uses a process called transient detection to determine where the beats are. The program slices the file into segments, placing a marker before the major transients (peaks).

Some programs also superimpose a tempo grid, placing a slice marker at note intervals (such as every quarter note, eighth note, or 16th note). Markers can usually be adjusted manually, but you rarely need to touch them — the automatic marker placement is generally dead-on in all of the programs surveyed here.

Keep in mind that in most cases, the audio file is not actually being segmented. Rather, the program creates and modifies a list of the markers, pointing to time positions within the original audio file. It's that list of marker times that gets manipulated when you change the tempo. Slicing not only makes it simple to change the tempo of loops but it can also let you quantize loops, derive groove templates from audio files, and perform wholesale drum and instrument replacements. (These programs also offer separate pitch-shifting functions so you can properly match pitches as well as tempos.)

Think of the loop as a kind of musical building block consisting of the original WAV or AIFF audio file along with the slice marker list and usually other information, such as the detected tempo or assigned key. Manufacturers use proprietary technology to implement this shiftable loop package; the REX2 and Acidized formats are supported by some of the originators' competitors. As you'll see, the need for preformatted samples is starting to disappear. (See the table “Looper Specs” for a list of supported file formats and other details.)

Most of the programs in this roundup are available for PCs with Pentium processors running most of the recent versions of Windows, including 98, ME, 2000, and XP. Three of the programs run on Power Macs with Mac OS 8.6 or higher.

This article omits a number of me-too or junior-edition programs, and it centers on the middle and upper ranges of the price and functionality spectrum. (See the table “In Review” for a list of the programs that have received full reviews in EM.) All the programs in this roundup are multitrack layering environments with the exception of ReCycle, the one that started it all. (You'll also find an alternative approach to loop manipulation in the sidebar “Ain't That a Groove.”)

RECYCLE (MAC/WIN)

Propellerhead Software (maker of ReBirth) started the loop-slicing madness back in 1994 with the original ReCycle. The EM editors liked version 1.0 so much they gave it an Editors' Choice award the following year. ReCycle 2.0, released in 2001, keeps this venerable tool relevant in the 21st century.

Designed as an adjunct utility for audio-editing and multitrack software, ReCycle pretty much does one thing: it offers better time shifting through loop slicing — and it slices loops exceedingly well (see Fig. 1). Propellerhead has addressed a number of the original version's shortcomings — for example, ReCycle now handles stereo files — and the company has kept the program focused, fast, and simple.

ReCycle lets you adjust the tempo of any loop and export it as a new WAV or AIFF file. Make sure you remember to select Transmit as One Sample from the Process menu when you want a single file. Otherwise ReCycle's default settings will cause it to save each segment in the loop as a separate audio file. If you have a sampler, you can then load the slices into a new preset and trigger the slices using any sequencing software. ReCycle even exports a Standard MIDI File beat map for that purpose.

Once a groove has been broken down to the component drum hits and their sequence of Note On times, you can easily adjust the tempo, quantize the performance, or replace any of the sounds.

ReCycle's proprietary REX2 files can be imported as a single audio track into a REX2-compatible sequencer (such as Reason, Emagic Logic Audio, or Steinberg Nuendo or Cubase VST) and played back with control over the tempo. According to Propellerhead, REX2 support in Mark of the Unicorn (MOTU) Digital Performer is forthcoming.

ReCycle supports direct SCSI transfer for major hardware samplers, and it offers MIDI sample-transfer capability and special Akai-format support. (ReCycle is the only program in this group that provides specific sampler support.) The software includes a handful of basic DSP processes, such as normalization, DC-offset correction, real-time EQ, compression, and pitch shift.

ReCycle ran without a hitch during my tests. If you've ever used sound-editing software, it'll take you ten minutes or less to figure out how to work with the program.