Practical Phrase Sampling For Modern Music Production: Part 3

In the final part of this series, Oli Bell gives you some practical tips and tricks on looping, re‑grooving and time‑stretching. This is the last article in a three‑part series.

Over the last couple of months we have looked at what features to consider when buying hardware for phrase sampling, where to find usable sounds and how to get them into your sampler. Well, what now? In this final part, I'll be looking at the techniques you'll need for constructing tracks using sampled phrases and, in particular, breakbeats.

Breakbeat Basics

Possibly the most frequently used type of sampled phrase in modern music is the breakbeat. Breakbeats (often shortened to just breaks) are sections of one or two bars, often taken from funk and soul records, where the music breaks down such that only the drummer or rhythm section is playing. Such sections of records were often used to give the listener a pause in the groove and to provide some musical variety.

DJs such as Kool Herc and Grandmaster Flash, who played New York block parties in the late seventies, noticed that the dancers went wild when this part of the record played. So, using two copies of the same record, they repeated such sections indefinitely, recuing each record while the other was playing and crossfading between them as necessary. Of course, with a sampler it is much easier to extract and loop breaks, allowing you to use them as the basis of a new track.

If you decide that you want to use a breakbeat (or any looped phrase, for that matter) as the basis of your track, then the first thing to do is make sure that the sample is topped and tailed correctly. But, before you even think of doing any editing, save a copy of the original sample! Believe me, getting into the habit of making regular backups will save you a lot of hair pulling.

Firstly, make sure that the beginning of the sample is trimmed as close as possible to the start of the phrase — in the case of a breakbeat this will usually be just before the kick drum at the beginning of the first bar. If your sampler has graphic editing, use the zoom function to get the start point of the sample in nice and close. Even when you've got graphical editing, though, you should still be sure to keep listening to the sample as you're editing — your ears should be the final judges of any edit, so use them.

If you are trimming solely by ear, however, it can be difficult to tell if you've trimmed all the dead space from the beginning of the sample. In this case, I always suggest pitching the sample right down (by one or even two octaves) while editing, as any empty space before the first beat will be much easier to identify in this way.

When you've sorted out the beginning of the sample, flip to the end and remove any redundant audio. It's a good idea to leave an extra beat at the end, often the first beat of the bar after the section you wish to use — this allows you a little freedom when attempting to get the sample looping smoothly. While you're trimming the end point, keep retriggering the sample by hand to check that you are left with the correct sample data.

Looping The Loop

When the sample is topped and tailed, it's time to set it looping. While it is possible to use the loop function built into your sampler, this type of looping is designed mostly for use when multisampling, extending the sustain portion of a sample for as long as the respective triggering note is held. However, when looping breakbeats or phrases, this on‑board looping has drawbacks which render it pretty much useless for creating the basis of a whole track. For a start, if you're working on a track and decide that you want to play it from the middle, then the sample wouldn't sound, as it would have been triggered earlier in the song. Also, the speed of the loop running freely will inevitably drift in timing against any parts triggering from the sequencer, and will do so in a slightly different way every time you play the track.

While many drum sample CDs give nominal bpms, these are often not accurate enough to use for looping the samples in your track.In short, the only sensible way to loop a breakbeat is by retriggering it every time it is needed. With most sequencers it is a simple matter to copy the trigger note however many times it is required throughout the track. If you've left a little bit of a longer tail on the sample than you need, then be sure to end each sequenced trigger note just before the next begins, and check that your sampler is set to receive MIDI Note Off as well as MIDI Note On messages.

The next thing to do is to match your sequencer's tempo to that of the loop, in order that your sequenced notes will retrigger the sample at just the right point to get it looping smoothly. If you know the tempo of the loop you are using, then you can simply enter this into your sequencer and you'll be most of the way there, but if you don't, then you'll just have to set the sequence going and match the tempo manually, gauging the effectiveness of each tempo adjustment by ear. In fact, even if you know the nominal tempo of the loop beforehand, you should still experiment with slight adjustments to this to check that you definitely have the best match — many bpm values given on sample CDs are rounded to the nearest whole number, for example.

If the sample has been trimmed correctly, and the tempo matched satisfactorily, the loop should repeat smoothly. If you have any problems getting the looping smooth, then try tweaking the envelope parameters for the sample's amplifier to make the transition a little more gradual.

Speeding Up & Slowing Down

Up to this point, I've assumed that you're wanting to use the loop at its natural tempo, but that's often not the case. Many people find themselves wishing to incorporate a loop at one tempo into a track at another, for example. There is software available which caters for this need — Sonic Foundry's Acid and Bitheadz's Phrazer, for instance — but this is often beyond the reach of the musician on a budget. Without such a program, the simplest way to achieve tempo‑matching is to change the pitch setting of the new sample, until its playback speed is in line with the track. The catch, of course, is that the required shift in pitch will not always sound appropriate.

Both Akai's MPC2000XL and Yamaha's A5000 have specific editing options for dividing up loops into shorter segments.

Yamaha A5000 Sampler.

Many modern samplers and audio editing programs now provide time‑stretching algorithms which can lengthen samples without pitch‑shifting. These usually work by replicating or deleting blocks of sample data, and crossfading at the edit points to make them as seamless as possible. Even though the quality of time‑stretching algorithms can vary considerably, they can often work brilliantly if the amount of time‑stretch is modest and can be particularly successful with samples which have few sharp transients — bass lines, for example.

Drum loops tend to not fare so well, however, especially when stretching the length of a sample beyond 10 percent or so, as you get flamming starting to creep in. With large stretches, the sampler has to work harder to fill in the gaps opening up in the sample data, and the sound begins to get quite grainy, though not without potential for some good sonic experimentation! Try stretching a loop, recording the result, resampling, then time‑stretching the resultant sample back to its original length — the digital colouring and rubbish that is introduced might be just the inspiration you need.

Another way in which you might attempt to keep the pitch of a sample constant while changing the length, would be to pitch it down within the sampler and then correct this pitch‑change with a real‑time pitch‑shifting processor. Pitch‑shifting technology has been available for many years now, so there are some good algorithms about — even if your pitch‑shifter is a bit dodgy, the graininess which it produces may be more desirable than that of your time‑stretching algorithm, so it's worth a try.

Breaking It Down

If you're working with drum loops, there is another way to match them to different tempos and grooves. The sampled phrase can be cut up into sections, each triggered from a different MIDI note, which can then be used to re‑assemble the pattern at the new tempo.

If you use a computer for music, there are many pitch‑shifting and time‑ stretching processors available with which you can match your sampled phrase to the key and tempo of a track.This process can be very effective, but it can also be time‑consuming. Many musicians use Steinberg's popular Recycle software to ease this chore (see the box on this page for details), but that doesn't mean that you can't cope quite adequately using your sampler's own editing facilities, if you have sufficient patience. My first step when doing this is always to make as many copies of my original sample as I plan to have final slices of it. An average one‑bar drum loop might need as many as sixteen or more copies, for example. Rename each one with a number, for example Drumloop 1, Drumloop 2, Drumloop 3, and so on. Next, edit the beginning and end points of each of the copies so that each successive element is isolated — as this is a drum loop you might trim Drumloop 1 to keep just the first bass drum hit, while Drumloop 2 might be trimmed to keep the hi‑hat hit immediately after it, and so on. Carry on until the end of the original sample and you should have one short, trimmed sample for each of the individual elements.

Now, you need to recreate the phrasing of your original loop. For this, set up your sampler such that you can play any of the original chopped sections alongside the original complete version, but with each sample triggered from a different MIDI note. Different samplers achieve this in different ways, but there are a couple of general setup considerations to bear in mind. Firstly, you'll have to make sure that each of the edited samples plays at its original pitch, even though they are all triggered from different notes. Also, it's usually best to set the sample‑triggering of the slices to 'one‑shot' mode, where samples are triggered in full regardless of the length of their MIDI trigger notes.

The first task will be to set up the original sample to loop smoothly, using the techniques I've already described, to ensure that your MIDI trigger notes are placed correctly relative to your song's measures. Once you've got the loop going, try playing along with it by triggering the slices from your keyboard. Do a few trial runs to get the feel of the timing, and then record your performance onto a new sequencer track. Quantizing to sixteenth or thirty‑second notes may help to tidy things up here if you don't trust your own timing. When the trigger pattern is recorded, shunt individual notes back and forth a few ticks at a time until the loop replays how you expect it to. If you wish to keep the exact dynamics of the original loop, make sure that all your MIDI notes are at maximum velocity, and that any velocity sensitivity in the sampler is at its minimum setting.

When you have managed to get the fragments triggering in pretty much the right places, try muting the original sample. Hopefully, your programmed version should now be at least a passable imitation of its forebear. Now try adjusting the tempo of your sequencer — it can be very liberating to be able to increase or decrease the tempo of the loop without the pitch changing. If you decrease the tempo, you may find that the gaps between the samples will seem unnatural, but you can partly overcome this by adding sampled 'air' underneath the new loop. I find that the the light crackles of the run in (or out) of LPs, or quiet breaks in live recordings (classical LPs being a personal favourite) are good for this use. Furthermore, ambience of any type can help to unify bunches of sliced samples into a complete loop.

Shuffling The Pack

Of course, there are other reasons for slicing up a drum loop, besides wanting to use it at a different tempo. Why not change the programming of the loop or add a fill? If you use extra beats or hits from the same loop, then they'll often work with it in spite of sounding a bit rough‑edged on their own. You can even reprogram the parts into a new sequence.

Though reordering of sampled slices is perhaps most commonly done with drum loops, many other samples can also be processed in the same way. If the result is interesting to listen to then it doesn't matter whether it sounds natural or not. In fact, the sound of instrumental or vocal samples chopped about unnaturally is normal in many modern styles. Any sampled riff or phrase — bass, guitar, sound effects, and particularly vocals — can be subjected to the editing scalpel and creatively reordered.

Try lifting a vocal phrase from a sample CD or other source — in most good dance music shops it's quite easy to find 12‑inches filled with a capella tracks specifically pressed for remixing, for instance. Cut the vocal phrase into its component words, in exactly the same way as we treated the drum loop earlier. Once again, you can now spread out the words to fit a different tempo, should you wish, possibly applying a slight timestretch to some of the chopped words to create a more convincing result. However, you can also now rearrange the slices to form a new sequence, which will not only create a whole new feel to the vocal but often new meaning as well. And why restrict the slicing resolution to just words? Cut each word into its component syllables, and try adding a change in pitch to individual syllables, or use different effects for each syllable. Or stretch, move and repeat them to create a new rhythm or strange delivery — need I say "re‑ee‑wind"?

Bass lines also lend themselves well to slicing: try cutting up a favourite bass line into one‑ or two‑note sections and making up a completely new loop of your own. A good tip is to pull out the little phrases that are unique to the bass — slides, pats or funky bits of finger and string noise — as these sounds can be difficult to program convincingly. They can be looped into new riffs or just added to your programming for extra realism or atmosphere.

Chopping individual chords or riffs out of piano, keyboard or vibes parts is equally effective. Try to remove a couple of different kinds of chord — one major and one minor, for instance — and use the resulting samples both straight and pitch‑shifted to create new sequences and changes. You could even try slicing the part at random intervals to see what results come up. You might just come up with a really great hook for your track.

An Ear To The Future

This short series should have you well on the way to successful phrase sampling. But remember, there are no hard and fast rules for sampling, so never be afraid to experiment. If something sounds good then it usually is good, so why not use it? While a great sampler, great samples and great technique can be really useful, none of these will make up for not using those things attached to the side of your head, for if you really do use your ears then even the most lo‑fi kit is unlikely to stand in your way.

Loop Processing With Steinberg's Recycle

The Propellerheads' Decks And Drums And Rock And Roll contains many good examples of creatively sampled vocals.

Steinberg's loop‑processing package Recycle came as a bit of a godsend to sample freaks and quickly found itself a welcome home in the dance producer's arsenal. It provides an easy, hassle‑free way to automatically chop up loops into their component parts.

You simply import the sample in question — a number of common sample formats are supported — and then let the program find where it thinks the individual elements are. Though it's usually pretty accurate at defining the slices you want, you are given the tools to tweak its automatically generated slice points, and also to add points of your own. Once this has been done to your satisfaction, the slices are transmitted back to your sampler via MIDI or SCSI as individual samples mapped chromatically. Finally, the program creates a MIDI file that plays back the slices in the correct order and timing, allowing you to edit or change the loop's sequence or tempo. For further details of the software's operation, refer to Paul Farrer's review in SOS May 1995.

Adventures In Pitch & Time

Because pitch‑shifting and time‑stretching have been used so much for making sampled loops and phrases sit together, the sounds that these processes produce have now become characteristic of many modern music styles. This means that pitch‑shifting and time‑stretching are now freely usable as creative effects.

Comparatively subtle shifts in pitch — a few semitones either way — can be very effective in bringing about tonal changes, especially with percussion. For example, pitching snares up slightly sharpens their impact, whilst pitching down whole drum loops can give a fatter, dirtier feel. If your sampler responds to pitch‑bend information, then try wiggling the pitch‑bend wheel of your controller keyboard while different samples are playing. Some samplers even let you route an LFO or envelope generator to the pitch of the sample, so that you can program pitch manipulations to happen automatically.

Large shifts and stretches are harder to pull off without sonic side effects, but that could well be an advantage if you're into creative processing. Large upward pitch‑shifts create a 'munchkinisation' which can be useful, while large downward pitch‑shifts or extreme time‑stretches create grainy results which have endeared themselves to many dance producers — perhaps the most notable example being Fatboy Slim in the breakdown of 'The Rockafeller Skank'.

One particularly useful technique is combining a time‑stretched or pitch‑shifted version of a sample with the unprocessed audio. Pitch‑shifting a vocal phrase through a perfect fifth, without time‑stretching it, can create a lovely harmonised effect with the original sample, for example. On the other hand, playing a drum loop at half or double speed against an unprocessed version of the same loop can add a whole range of atmospheric grunge or odd percussive effects.