Loops | Under Construction

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FIG. 1: In this Apple Logic Pro 9 reconstruction of kit 7 from Big Fish Audio Hip Hop Exotica 2, comp tracks are used for the brass, bass, and kick parts.

Writing EM''s “Sound Advice” column for the past several years has loaded my hard drive with commercial sound libraries. My collection contains hundreds of thousands of audio files. Is that a blessing or a curse? I won''t weigh in on that controversy, but in creating Web Clips for the column, I have learned a few things about what does and doesn''t work. Here are some ways to get things started, keep them rolling, and speed up the most tedious parts.

By sound library I mean a collection of loops and phrases for use in creating or augmenting songs (not a sampled-instrument library). Although sound libraries take many forms, they are usually organized by tempo and, for pitched material, by key. Often they are also grouped as construction kits containing compatible elements that you can use as a song starter. I''ll begin there.

Many construction kits include a short demo song. One of the best ways to learn how the author intends the library to be used is to reconstruct one of the demos. Depending on the complexity of the kit and the length of the demo, the process should take less than an hour, and it''s well worth doing at least once. I do this every few months, and it always sharpens my ear and my ability to analyze a mix. It''s also a good way to convince yourself that the demos actually can be made from the parts provided in the kit (or not).

The details of reconstructing the demo depend on the features of your DAW, but here are the essentials: You''ll need a way to easily switch back and forth between auditioning the demo and the reconstruction so assign the track holding the demo to its own bus, route a submix of all the construction-kit tracks to a different bus, and set up a button or fader on your MIDI controller to alternately mute one or the other of the buses. Don''t configure the fader to adjust the bus volumes in opposite directions because you''ll want to adjust them individually for a more accurate comparison.

Use a separate track for each loop and one-shot in the construction kit or devote a track to each instrument (bass, piano, vocal, drum kit-piece, and so on) and then sequence all clips for that instrument on the same track. With the latter method, ensure you have separate tracks for instruments that overlap—for example, use separate tracks for rhythm and lead guitar, acoustic and electric piano, and lead and background vocals. If your DAW supports comping from different takes, as do Apple Logic Pro and Propellerhead Record, you might prefer to use comp tracks for instruments with multiple clips and then use different comps to fly in the right clip. Ableton Live users will find it easiest to insert the clips in Session view slots and then launch clips to create the arrangement.

You''ll speed things up considerably by setting markers to delineate parts of the song and to mark places within those parts where you notice changes. Looping these smaller sections is the easiest way to build your tracks. Point your DAW''s browser to the construction kit and audition its files for parts that stand out in the demo. When you find a match, drag it to the appropriate track (see Fig. 1 and Web Clip 1). If your DAW''s browser is not well-suited to that task, you might consider a third-party file-browsing utility such as Iced Audio AudioFinder (see sidebar Tools of the Trade”).

When you''ve reconstructed a section of the song, loop the song up to that point and spend several passes comparing your version to the demo. You''ll undoubtedly hear something you missed or a part that doesn''t match exactly, and by the time you finish the song, you''ll have most of those errors and omissions fixed. If you find parts in the kit that aren''t used, that''s often a tip-off that you''ve missed something. Listen to the part by itself and then listen for it in the demo.

Often the parts in the construction kit match the levels and panning in the demo mix so you can keep them centered and at 0dB, and adjust the two output buses to match levels. If a part does jump out in contrast to the demo, fix it, but don''t waste time obsessing over the mix.

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FIG. 2: I''ve used AudioFinder''s Sample Tool to slice an 8-bar bass stem into 2-bar slices. The red gridlines are at 2-bar intervals, and the yellow-handled markers indicate the slice points. The slice marker at 4.1 was deleted to preserve the 4-bar phrase.

A fast and effective way to generate variations on a song you''ve created or reconstructed from a construction-kit demo is to generate stems from your tracks and then slice them up and reorder the slices. Try to make all the slices the same length—typically, one or two bars as suits the music—but make exceptions when a cut interrupts a musical phrase. You may want to work on individual choruses in longer pieces.

Most DAWs will export stems from a project. In Live, either consolidate each track or use the Render function to export stems for all tracks in one go. In Logic, the File menu offers Export All Tracks as Audio Files, which creates stems the full length of the Logic project so you''ll want to set Logic''s end marker to the true end of the song. Record''s implementation is particularly robust. After choosing File > Bounce Mixer Channels, you can select which channels to include, bounce the channels pre- or post-mixer, set the file type, and choose to bounce the whole song or only the current loop.

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FIG. 3: Slices from a 6-part arrangement in Ableton Live occupy Session view Clip slots (top). Three Scenes are captured at the bottom, and the Rev 4 clip is playing along with the third captured Scene.

Many DAWs, samplers, and sample editors have tools to cut audio files at regular intervals or into a fixed number of slices of the same length. I use AudioFinder''s Sample Tool window to create equal-length slices based on the number of bars and the note division I provide. I use the Sample Tool''s Set Sound Length option, which pads or trims the stem to the right length based on tempo and bar count. (Logic''s renderings occasionally come up a few beats short, and checking the stem lengths is not a bad idea no matter how they''re generated.)

If you want slices longer than one bar, you''ll need to fool many applications—including AudioFinder—by lying about the number of bars and then making 1-bar slices: Divide the number of bars by two for 2-bar slices, by three for 3-bar slices, and so on. Once you''ve specified the grid and the application has inserted slice markers, eliminate any slice markers that interrupt a musical phrase (see Fig. 2). Next, export the slices as separate audio files.

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FIG. 4: In Groove Menu mode, Spectrasonics Stylus RMX assigns separate notes on MIDI channels 1 through 8 to trigger the grooves in RMX''s eight parts.

Live''s Session view is ideally suited for looping, triggering, and rearranging slices. Create a track for each stem and load the slices from the stem into consecutive Clip Slots. Launching a Live Scene loops a single slice from each stem, and launching individual clips substitutes different slices from the corresponding stem. When you have a variation you like, use Capture and Insert Scene from the Create menu to insert a new Scene from that variation (see Fig. 3). Finally, click the Global Record button to sequence an arrangement from your captured Scenes.

Spectrasonics Stylus RMX in Groove Menu mode is another excellent tool if you have Propellerhead ReCycle to turn your stem slices into REX2 files. For some stem slices, ReCycle may ask to move the left or right end locator; answer No because you''ve already trimmed the slices. Enter the stem length in ReCycle''s Bars count, configure your ReCycle slices, and save the file to a new folder named after the stem. When you''re finished, you''ll have a folder of REX2 files for each stem. Move them all to a new folder and drag that folder to the Spectrasonics SAGE Converter utility window.

The next time you open the RMX browser, you''ll find a folder with your project''s name in User Libraries, and in that folder you''ll find folders holding the slices for each of your stems (see Fig. 4). Use a separate RMX part in Groove Menu mode for each of these folders. Consecutive MIDI notes starting at C3 (C2 or C1 if you have a huge number of slices) on the part''s MIDI channel will trigger the individual REX2 files. The REX2 slices within those files are available for all of RMX''s creative processing, including tempo matching, Edit Groups, insert and send effects, and Time and Chaos Designers.

Many samplers will slice and key-map the stems for you. In Native Instruments Kontakt, import the stem into a Kontakt instrument, select it in the Mapping editor, and click the Wave Editor tab. Turn on the Wave Editor''s Grid section, choose Fix mode (the default), select the maximum width (1/1—a whole note), and set the Grid BPM to the real tempo divided by the desired number of bars per slice. For example, for 2-bar slices, divide the tempo in half. Next select the Sync/Slice tab (but don''t turn it on), click the first slice in the waveform display, and Shift-click the last slice—this selects all of the slices. Finally, click-and-drag the slices to the Mapping Editor window to map them to the keys you want to use as triggers. As long as you leave playback (Mapping Editor Source) in DFD or Sampler mode, the slices will play at their true tempo.

For a more hands-on approach, Native Instruments Maschine is hard to beat. Use its sample editor''s Slice tab to slice your stem. In addition to grid and transient slicing, you''ll find a convenient Split mode that lets you create four, eight, 16, or 32 equally spaced slices. Once you''ve set up slicing, clicking the Apply button generates a Pattern that steps through the slices. You can then generate your own Patterns for as many as 16 sliced sound files within the Group.

The Maschine hardware''s pads trigger slices for their full length, which makes it easy to record and edit Patterns on the fly. Select a sound, record trigger notes, select another sound, record more trigger notes, and so on until you''ve built up a Pattern you like. Load different Groups with alternative sounds and install Patterns in Maschine Scenes to create songs. You can do everything from the hardware.

You''ll get only so far with the loops and one-shots provided in a construction kit. To generate something truly your own, mix and match material from different sources, process and modify loops, and layer in some of your own material. Mixing and matching material from different sources—other construction kits or bonus samples in the same library, as well as material from other libraries—is much easier with a good browser. Some DAWs and samplers make that process fast, easy, and nearly transparent, but if yours is not among them, a full-featured third-party browser will save you lots of time and frustration.

Once you find material you want to use, you''ll confront three issues: pitch, tempo, and groove. Fortunately, full-featured DAWs include tools to handle all three, but the results will vary depending on the source material.

If you do a lot of pitch manipulation on monophonic audio parts, consider investing in a tool designed specifically for that such as Celemony Melodyne or Antares Auto-Tune. For tempo and groove manipulation of audio, you''ll sometimes get better results by first slicing (on beats or transients, depending on the material) and then manipulating the slices and the generated MIDI files that play them. Having said that, recent advances like Logic''s Flex Time Editing, Live''s upgraded Warping Engine, and Propellerhead Record''s Tempo Scaling and ReGroove mixer deliver excellent results without the need for manual slicing.

The viability of playing or sequencing your own parts depends on your chops and the instruments at your disposal, but the more the better. Processing and modifying the material at hand is an intermediate option, and here are some ways to start.

If you''re using MIDI drum loops (and many libraries include at least some MIDI parts), two easy options are swapping kit pieces and moving some hits from one kit-piece to another. You might try something as radical as replacing an entire acoustic kit with an electronic kit, or vice versa. That''s a great way to set off one part of a song from another. On the less-is-more side, add a second kick drum to your kit and move some of the original kick hits to it, or layer a crash cymbal with a sound effect.

For an audio drum loop, the first step is to slice it up into individual hits, many of which will include several kit pieces. You can use a utility like ReCycle, but your DAW or sampler most likely has tools for this. Whatever tool you use, it''s important to audition the resulting slices one by one to ensure that you didn''t accidentally cut into the beginning of the next sound, as indicated by a click at the end. Fixing that is as simple as adjusting the slice''s endpoint, but the beginning of the next sound''s slice may also need adjusting if its onset is severely clipped; the MIDI note that triggers that slice will then need to be moved accordingly. If there are many such problems, it''s easier to manually adjust the slice markers and re-slice.

Once you have a sliced audio loop, observe which slices have similar sounds—kick alone, kick and snare, closed or open hi-hat, and so on. Moving some MIDI trigger notes vertically to swap similar sounds is a subtle way to vary a loop from one pass to the next. For more radical surgery, swap dissimilar sounds. You might also replace or layer some sounds with new samples. An easy way to do that is to copy the MIDI trigger clip, delete all but the wanted triggers, and use the new clip (adjusting the note pitches but not the note positions) to play a sampler or drum synth (see Web Clips 2 and 3).

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FIG. 5: Use Reason 5''s Dr.OctoRex loop player to switch between eight REX2 loops. The Alt function is used to shuffle like-sounding slices, as seen in the third pass (bottom).

Slice swapping is also an effective tool with bass loops. Reason 5''s Dr.OctoRex makes fast work of that while letting you simultaneously switch loops as the song evolves. Load a Dr.OctoRex with one or more bass loops. Select a loop slot, click the Programmer''s Slice Edit mode button, and click the word Alt in the loop display. That reveals a bar-chart overlaying slices—click and drag in the bar chart to assign any slice to one of four Alt groups. When you play the loop or send a pattern to a sequencer track, slices from the same Alt group will be randomly swapped (see Fig. 5 and Web Clip 4). Keep in mind that you can load the same REX2 file into several Dr.OctoRex slots to use different Alt configurations (including no Alt assignments).

Random swapping of similar slices is a quick way to create variations, but some will work better than others so select the best and trash the rest. Swapping slices manually by dragging notes vertically in a piano-roll note editor gives you complete control. In order of decreasing subtlety, try swapping slices with the same pitch and articulation, the same pitch but different articulations, pitched an octave apart, and pitched a perfect-fifth apart.

Slice swapping is less useful for leads and polyphonic parts because you usually don''t want to mess with the melody or chord changes. (But don''t overlook it as a way to take things a bit outside.) Slicing is useful for melodic and polyphonic material for time manipulations—tempo changes and groove matching—and for part doubling.

One way to double or replace a monophonic lead part (vocal, horn, lead guitar, and so on) is to play and record a MIDI version of the part as close to the original timing as you can, then groove-quantize the new part to the original. Slicing the original is the easiest way to capture its groove (although most DAWs will groove-quantize from an audio part by analyzing its transients). Once you''ve sliced the original part, you also have the more tedious alternative of adapting the resulting MIDI file (the one used to play the slices) to play the doubling instrument by moving the MIDI file''s notes to the desired pitches. Of course, you''re not limited to doubling; you can create harmony tracks and different leads.

Several software tools automate that process. Antares Auto-Tune and Celemony Melodyne make quick work of monophonic part doubling and pitch manipulation. Harmonizers like Antares Harmony Engine and Zplane Vielklang create multipart harmony on the fly. Melodyne Editor will (up to a point) let you analyze and manipulate the individual voices of polyphonic parts.

Beyond the topics covered here, consider adding effects processors—especially the more exotic ones—for creating new sounds from old, using the arsenal of sound-design tools in your DAW and sampler, and manipulating the tempo. One thing I''ve learned is that the song is never finished. When you think you''ve hit the wall, put the project aside but not in the trash. Some new idea or sound will come along to take it in a different direction.

Each of these software tools could save you hours of hard labor. Also check out “Essential Utilities” in the December 2008 issue of EM.

Antares Auto-Tune Evo
(Mac/Win, $199)

Thanks in part to the “Cher Effect”—and its more recent incarnation, the “T-Pain Effect”—the name Auto-Tune has become synonymous with pitch correction. The latest incarnation presents monophonic parts as note and transition lines in a piano-roll-style display, lets you change pitches by dragging, and includes many of the formant-munging and throat-modeling tools from Antares AVOX Evo.

Celemony Melodyne Editor
(Mac/Win, $299)

Melodyne offers pitch correction similar to that of Auto-Tune, but it lacks the latter''s throat-modeling features. What Melodyne adds is the ability to peer inside polyphonic material and shift individual notes. That process is time-consuming and not quite perfect, but in many cases it will do, and it is indeed revolutionary. Also, it''s a handy tool for analyzing chords even when you don''t want to mess with them.

Iced Audio AudioFinder
(Mac, $69.95)

If your computer is a Mac and you have a large audio library, AudioFinder is a must for browsing. When you point it to a folder or a Scan Set of disparate folders, its browser will display all audio files of all types nested within. You can then include or exclude files matching search terms in their filename, folder name, or metadata; step through the list sequentially or at random flagging favorites; and copy, move, or alias any selection of files to any location. In addition, AudioFinder is bristling with tools for audio processing (including AU plug-ins), file slicing, and automatic format conversion.

Propellerhead ReCycle
(Mac/Win, $199)

If you want to convert audio files to REX2 format, ReCycle is the only game in town. While many DAWs, samplers, and loop-oriented applications have their own sliced-loop format, most also support REX2 files.

Seventh String Software Transcribe
(Mac/Win, $50)

When you need to analyze polyphonic material to sort out the notes in a chord, Transcribe can do the heavy lifting. It identifies the prominent harmonics on a keyboard graphic and suggests possible chord names. When you can''t quite decode some elusive inner voicing, Transcribe will provide the necessary nudge. It also offers credible time-stretching for easier transcription of blisteringly fast lines.

Len Sasso is a freelance writer and frequent EM contributor.