Get Into the Loop

Loop production has been a mainstay for electronic, dance and soundtrack music for years, but new tools make it more appealing to songwriters than ever before

Get in the Loop

The Dr. REX module in Reason displays a REX file’s audio, The vertical lines near the waveforms indicate the “slices.” Each slice is triggered by the accompanying MIDI file in the lower part of the screen. These MIDI notes can be edited to change the groove.

Sony ACID was the first program to offer realtime pitch and tempo manipulation, features that have become part of the mainstream.

The Apple Loop Utility can embed an audio file with meta data that tracks pitch and tempo (The blue bars show hit points). It also allows users to add searchable tags for genre, mood, and more.

FORMATS Loop Libraries come in several formats Here are the most popular: ACID Loops: ACID uses .wav files that are embedded with meta data, which indicates the audio’s original tempo and pitch. ACID software can automatically tag a file imported into it. In addition to Sony’s own products, ACID files can be read by Cakewalk’s SONAR and others. REX: Propellerhead’s REX format actually consists of two elements. First is the audio file, which is divided up into sections called “slices.” This audio file is paired with a MIDI file that uses a separate note message to trigger each slice. Apple Loops: Apple Loops, which work with GarageBand, Logic and Soundtrack, are AIFF files embedded with meta data that tracks a loop’s original pitch and tempo. Many Apple Loops can work as both audio and MIDI files. The latter option lets you change the sound and edit the performance of the loop to suit your song. Standard AIFF, .wav and MP3 files: Music software is becoming increasingly savvy when it comes to analyzing tempo and pitch, making it easier to work with standard audio files. Ableton Live and Sony ACID can integrate “untagged” files into the mix, and offer tools to help you fine-tune the loop and identify its hit points. This works best if the audio file is short. Apple’s Loop Utility lets you open a file, define its tempo and pitch, and code it with tags for searching. Similarly, Propellerhead’s ReCycle lets you turn standard audio into a REX file.

The use of pre-recorded loops became popular in the early sampler era of the 1980s and helped define the sound of hip-hop, house and other dance genres. But back in the day, these short snippets of music weren’t really useful for producers who wanted to match the flexibility afforded by real musicians playing real instruments. Today’s software, combined with a huge array of libraries, let songwriters and producers of all genres use loops to write and produce unique tracks.

Software Tools

These days, almost all the mainstream digital audio programs offer loop-production features, but just a few years ago, loop construction was a specialized field that involved painstaking editing on a hardware sampler. When programs like Propellerhead’s ReCyle and Sony’s ACID (originally developed by Sonic Foundry) made it easier for mainstream musicians to work with loops by giving them more control over the tempo and pitch of pre-recorded material, a new industry of pre-recorded loop libraries followed. A whole new way of making music emerged; now, producers can assemble and arranging pre-existing material without ever picking up an instrument, And while that’s effective, it also led some more traditionally-minded songwriters to feel that loops— other than the occasional simple drum beat—were not useful to them. Today, however, sound libraries are becoming more varied and more flexible, allowing traditional songwriters to create complete tracks that have more of the nuance of a live performance. Before we look at these, let’s step back and look at how production software deals with loops.

Hit Points

Today, many tools are available for working with pre-recorded snippets of music: The original loop manipulation programs, like Sony’s ACID family (the flagship, ACID Pro, is now in its 6th edition) and ReCycle 2.1 (which creates a file format that’s compatible with Propellerhead’s popular music production suite, Reason 4) are still growing strong. These programs have had a major influence on music software in general: Programs like Cakewalk SONAR; Apple GarageBand and Logic; Ableton Live; Steinberg Cubase and Nuendo; Digidesign Pro Tools; and Mark of the Unicorn Digital Performer each offer various features that facilitate the use of loops with a minimal or no editing rom the user. But if you want to go beyond merely dragging a loop into a song and seeing if it works, it helps to know what goes on “inside the audio.”

In order to effectively adjust the time and pitch of a prerecorded audio file, the software must know something about the audio’s original pitch and tempo. This information is stored in the audio file in what’s called meta data. A file that’s compatible with ACID—known as an “Acidized” file—basically has a packet of data that tells of software the loop’s length (in bars and beats), its tempo and its original pitch. The Apple Loops format used by GarageBand, Logic, and Soundtrack employs a similar principle.

In either case, the software looks for important transients, or hit points, in the audio material. With a drum loop like the one shown on the following page, you can see how the waveform representing the sound gets higher (showing that the sound is louder) in spots where the main kick and snare hits occur. It’s by mapping these hit points that the software is able to speed up and slow down the audio.

If you’re working with a professionally prepared library, this happens in the background: Once imported into the software, the audio file will simply play at the song’s tempo instead of at the file’s original pace.

ReCyle uses a slightly different approach. Like ACID and GarageBand, ReCylce’s REX format looks for hit points; but instead of integrating these into a single unit, it “slices” the audio into segments, so that each hit-point is an independent sample; an accompanying MIDI file follows the groove in the audio file. When the program was first developed, it was intended for use with hardware samplers—you could load the MIDI file into a sequencer and send note messages to the sampler, with each key triggering a different slice. Speed the sequencer up, the the slices would be triggered faster. One cool thing about working with this format is that the MIDI file generated with the REX file can be altered; you can, for example, change a groove to create a fill or an ending by copying or moving one of the MIDI file’s notes, as shown in Reason (left). Many DAWs, including such as Cubase, Logic and Pro Tools 7, can also import REX files directly.

Building a Library

Commercial sample libraries still largely cater to dance, urban beats and trip-hop loops, but there are also many collections covering traditional styles like country, jazz, folk, Latin, and rock.

Though there is a growing market for downloadable loops, complete loop libraries generally come on DVD, which can contain more than 4 GB of data apiece. Many of these collections, however, don’t use all the storage on unique material. Instead, you might find one collection of loops, duplicated in a range of popular file formats. If, like most of us, you’re working with several different pieces of software, this is ideal. You might, for example, pull an a drum beat in ACID format into a song in SONAR, then open its REX version in Reason in order to process it through that program’s Dr. REX player. Note that some collections are designed for a specific format (Sony offers ACIDized files; Propellerhead offers REX files called Reason Refills; Apple sells Apple Loops, etc.). Third party vendors, however, often offer content in multiple formats.

Loop collections fall into three categories. General collections that cover a rage of musical styles can be pretty economical— you’ll find these bundled with many samplers and programs—but their disadvantage can be that you may only get one or two versions of any given loop. For example, you might find a blues shuffle with hi-hat, and a similar one with ride, but may not get any fills that go with that loop. That’s not necessarily a bad thing; adapting loops to suit your needs is an opportunity for you to add your own creative stamp onto what would otherwise be a static performance

Other collections focus on one genre or style. These can be restricted to one instrument, such as Sound Sense’s “LA Drums,” or they may offer a complete range of instruments for a style, as in an Best Service “Hip-hop Producer Packs.” The advantage of these genre collections is that the loops are designed to go together. For example, a Latin collection might offer a range of drum beats, basses, horn hits, and single instrument sounds that can be layered together or used on their own. These can be compiled in complete collections: IK Multimedia’s R. A. W. Universal Groove Kit Gold Edition comes with more than 42,000 loops and covers everything from hip-hop to jazz to country.

Finally, there are the collections created by specific artists and producers. Sony’s Bill Laswell Collection, for example, gives you a wide range of production elements from a producer who’s worked on projects ranging from PiL to James Blood Ulmer to Miles Davis. In a sense, using this collection is like sharing your production with Laswell.

You’ll also find libraries of loops by wellknown performers. Sony’s “Mick Fleetwood Total Drumming” delivers his signature style and sound. Another name artist in the Sony “loop” is bassist Rudy Sarzo. Submersible Music’s Drum Core program and library features a range of well-known drummers, and can synchronize with a DAW or can export loops—which include basic beats, variations, fills, and transitions— as REX audio files or as MIDI files.

Organizing Loops

While working with pre-recorded loops makes the production side of your job easier, it does involve one daunting task: organizing the material and being able to find it later. Fortunately, modern software offers some built-in database features to make life easier. Apple Loops can be tagged with information about the loop’s genre, sound, and more, and lets you search these tags from within Logic, GarageBand and Soundtrack. Other programs have similar database functions to help you search and organize your stuff.

If, on the other hand, you’ve ever tried to manually click through a DVD worth of 4-30 second clips, you know that it can get exhausting. A well-organized library can give you some clues. IK Multimedia’s aforementioned R. A. W. collection follows a naming convention that tells you the loop’s tempo. For example, a file called Rock_Drum_140.wav would have a tempo of 140 beats-per-minute.

One way to take control of your library is to consolidate all of your loops onto a hard drive. You can then organize the loops into folders, rename the files as needed with tempo information, and even set up a database to help you search them.

Creating and Customizing Loops

A good loop collection may offer plenty of variety right out of the box, but there will also be times when you’ll need to customize the pre-recorded material to meet your needs—or, create a loop library of your own.

Programs like ACID, the Apple Loop Utility, ReCycle and Ableton Live can do much of the work for you by analyzing the file and identifying hit points. When working with these programs, you must make sure to carefully define the beginning and the end of the audio loop so that software can accurately determine its tempo. These tools are are effective for converting audio you’ve recorded yourself into loops—you might, for example, harvest some bass lines from a track and save them as loops for other songs. If you’re working from a longer sound file, you may want to edit the and save the into smaller chunks before adapting it for looping.

Finally, know the limits of your software. Best results come when the original tempo and pitch of the loop are close to those in the song you’re working on. A 10-20 percent difference is workable, but too much of a “stretch” and you’ll hear audible artifacts. Then again, these can create a unique sound that might just add a little extra flavor to your production.