Sampling Techniques (Part 4)
How To Get The Most From Your Sampler
Tom Mclaughlin leads another expedition deep into sample country. This month: how to create stereo instruments from mono samples.
This month we're going to take a look at a few editing tricks to make mono samples sound a bit more like stereo. Of course, you can always pass a mono sample through a stereo effect such as a digital reverb to create the impression that the sample is placed within a stereo sound field.
Alternately, a mono output from your sampler can be split into two (with a splitter box or lead — easy to make up for about a fiver) then processed by two similar, identical or even completely different rack or pedal effects; say an electric guitar sample passed through two different overdrive or chorus pedal effects, both with slightly different settings and panned left and right through a mixer. Routing the same sound through two identical graphic EQs, one with odd numbered bands accentuated, the other accentuating the even bands, panned left/right always works a treat in helping to make a mono source sound a bit more stereo.
Manufacturers such as Orban and Studio Technologies both made dedicated mono-to-stereo synthesizers that do a good job of spreading a mono source between two speakers. Ultimately, however, if stereo is to be derived from mono sounds, they need to be either sampled with a stereo effect in the first place or the stereo effect added as the sample is recorded to tape.
Still, you don't have to possess a sampler with stereo inputs to concoct some interesting and musical stereo images. There are several sample editing techniques we can use to simulate stereo. None of these give true stereo but, rather, a 'mock' stereo effect that adds a spatial perspective and/or animation to mono samples. All your sampler needs is a stereo output (two mono outputs will do for sounds panned hard left and right) and the facility to pan or route samples to different outputs. Try these tricks for yourself:
The most straightforward method of creating the impression of stereo from a mono sample is to pan the same sample left and right and tuning one a few cents sharp, the other a few cents flat. Although simple, this really does have the effect of fattening up mono sounds while providing a stereo-ish image. This image widens as the sounds are more out of tune with one another. If the two versions of the same sample are detuned flat and sharp by the same amount, the human ear seems to average the two and hears them as relatively in tune.
|Sample 1||Full Left||- 7 cents|
|Sample 1||Full Right||+ 7 cents|
The exact amount of de-tuning will have to be judged by ear. I tend to work within a range of between 5-15 cents, rarely more. You will want to find an amount that creates a stereo separation while avoiding any phasing problems when collapsed into mono.
An augmentation of the above technique. In addition to panning the same sample left and right with the same amount of positive and negative de-tuning, modulation and/or automatic pitch bend applied to one sample or different rates of these applied to each sample will exaggerate the stereo effect.
When using modulation, pitch mod seems to give a more natural stereo effect. Depending upon the rate and intensity, this can range from a gentle chorusing effect all the way through to a manic vibrato. Filter, amplitude and panning modulation, if you have them, can also help to create a stereo image. Try pitch mod on one side and either no modulation or another type of modulation on the other side... and don't forget to try different rates as well as modulation delay amounts.
Some samplers sport envelope controlled pitch bend to control the pitch of a sample over time in much the same way as loudness and brightness are shaped with an envelope on synths as well as samplers. Nine times out of 10 pitch is affected by the same envelope as the filter. (I don't know why. A separate envelope for pitch is extremely useful — especially with drum and percussion sounds where the envelope curve for the filter and pitch can be distinctly different.) You may have to disregard the filter section of your sampler when affecting pitch with the envelope. For many sounds this won't be a problem. Getting the setting right with a pitch envelope can be tricky — something we'll take a closer look at in a future issue.
Starting the doubled sample in tune with itself, then making it grow out of tune through use of your pitch envelopes will have the effect of the sound starting out in mono and evolving into stereo as the two identical samples grow more out of tune with one another. (Remember to adjust the tunings with equal amounts of negative and positive detuning.) A short semi-tone or whole-tone slide to pitch — up one side, down the other side — often gives just the right separation at the start of notes to add more bite to brass and string samples. The slide must be very short, though; less than 1/10th second, otherwise it can sound a bit sloppy. On the other hand slightly longer pitch envelopes work better with choirs and vocal pad samples.
If we're on about Pad or Tone Loops — ie. sample loops with no material present before or after the loop points — simply copying the sample, reversing it, and panning one version left and one right is often all we need do to create a pseudo stereo image (see Figure 1). The same sound but moving in different directions. This technique works brilliantly with swirly synth, brass, string and vocal pad loops.
Depending upon your sampler, you may need to get in there and re-adjust loop points on the reversed sample. If you haven't any samples in your collection that fit the bill, you could always snip off the attack portion of a sample with a loop on which you'd like to try out this trick.
"...if you're willing to venture under your sampler's bonnet and get your hands dirty there are a number of multi-sample panning tricks that can open up new stereo soundscape possibilities to you..."
I believe I was the first to use this technique, at least on these British shores. I don't remember hearing adjacent members of a multi-sample overlapped and panned opposite sides to create a stereo effect in any of the Fairlight, Emulator, PPG or Akai library samples I'd been working with up to that time.
A few months after getting an S1000 in my hands I started to experiment with overlapping adjacent members in multisamples to see just how smooth a transition could be made. Up until that time the norm seemed to be that while two or more sounds could be layered in some samplers, they had to share the same 'keygroup' or keyboard range. On early samplers keygroups could not be overlapped in the same multi-sample and had to be 'butt joined' — one sample leaving off where the next started. I must say that I have the utmost respect for early samplists responsible for library samples — with no keygroup overlap or cross-fade to fall back on to smooth transitions.
As I'd suspected, overlapping adjacent multi-sample members to the max (ie. butt joining alternate samples mid-way between each) and panning them dead centre smoothed out any transitional bumps between samples, thickened the sound, and offered two loops of varying lengths playing simultaneously — which smoothed out questionable loops. But with alternate samples panned L/R/L/R and so on, a marvellous thing happened: suddenly my mono multi-sample sounded like it was in stereo!
To check this out for yourself you'll need a multi-sample with fairly evenly spaced samples. In Figure 2 below are listed typical multi-sample key ranges for both a mono configuration and a stereo configuration as suggested here; see also Figure 3.
Not all samplers react the same way to samples being transposed upwards. It all has to do with the Nyquist theorem. It's not as complicated as it sounds — frequencies higher than the maximum sample rate will become digital distortion, known as aliasing, which surfaces as mid to low frequencies being added to your sample totally unrelated to the sound at hand.
If the second from highest sample won't transpose up to the top note of the multi-sample you have several options:
• Leave it out. Make its top note the highest note it will playback without sounding too strange and listen to see if its absence is noticeable. You just might get away with it.
• Take the second from highest sample up as far as it will go, then double the top sample and detune as above.
• Reduce the sample rate (via sample rate conversion, in semi-tones if possible) of the next to top sample until it does transpose up to the multi-sample's top note. If it hasn't lost too much top end (reducing the sample rate reduces high frequencies) it might just fit back into the multi-sample as is. If the top end loss is more than you're happy with and you have the RAM, add the extra sample (you have saved the original next to top sample, haven't you?) to your multisample, taking up where the original starts sounding suspect due to aliasing.
The most obvious and straightforward panning arrangement for a mono multisample is to have the bottom of the keyboard pan sounds to one side, then pan things through centre and to the opposite side as you progressively play higher up the keyboard. Some samplers have this panning 'template' as an onboard option. But this really isn't stereo to my ears — the same mono samples are coming from the left output, right output or both. It also provides a most unnatural stereo image, with the bottom end panned one side and the treble the other side. This is usually fine with things like piano or string trio sample sets, but with little else to my ears.
With the the multi-sample arrangement described above, simply panning sounds alternately left and right will give you an effective stereo image — and the apparent size of your multi-sampled instrument(s) will be doubled to boot. However, if you're willing to venture under your sampler's bonnet and get your hands dirty there are a number of multi-sample panning tricks that can open up new stereo soundscape possibilities to you...
As an example, by taking the time to pan each Keygroup (or your sampler's equivalent) individually, sample sets can start with the lowest notes panned near centre developing to a wider stereo image the higher you play up the keyboard. Maybe it has something to do with my training as a recording engineer (with the kick drum and bass dead centre, balancing sounds with high frequency content left/right like one does for practically every stereo mix), but this sounds so much more natural to my ears than many other panning configurations. Try it — you'll like it.
On a panning scale of 50L/R, check out some of my fave panning 'patches' (the numbers 1-10 refer to Keygroups, as in the example of overlapping Keygroups above; they are paired to indicate that they overlap):
|Low||1) L05 - 2) R05||1) L10 - 2) R10|
|3) L10 - 4) R10||3) L20 - 4) R20|
|5) L15 - 6) R15||5) L30 - 6) R30|
|7) L20 - 8) R20||7) L40 - 8) R40|
|High||9) L25 -10) R25||9) L50 -10) R50|
|STAGGERED||STEREO POSITIONAL (L/R)|
|Low||1) L05 - 2) R10||1) L50 - 2) R10|
|3) L15 - 4) R20||3) L40 - 4) R20|
|5) L25 - 6) R30||5) L30 - 6) R30|
|7) L35 - 8) R40||7) L20 - 8) R40|
|High||9) L45 -10) R50||9) L10 -10) R50|
The 'narrow' and 'wider' stereo panning patches can also be layered on top of one another and switched between via velocity switching or cross-fading, which gives a wonderful widening of the stereo image the harder you play. You may have to adjust the velocity switch points to suit your playing style and/or gear:
|VELOCITY SWITCH||VELOCITY X-FADE||PANNING|
|0 - 90||0 - 110||1a) L05 - 2a) R05||soft|
|91 - 127||80 - 127||1b) L10 - 2b) R10||loud|
|0 - 90||0 - 110||3a) L10 - 4a) R10||soft|
|91 - 127||80 - 127||3b) L20 - 4b) R20||loud|
|0 - 90||0 - 110||5a) L15 - 6a) R15||soft|
|91 - 127||80 - 127||5b) L30 - 6b) R20||loud|
|0 - 90||0 - 110||7a) L20 - 8a) R20||soft|
|91 - 127||80 - 127||7b) L40 - 8b) R40||loud|
|0 - 90||0 - 110||9a) L25 - 10a) R25||soft|
|91 - 127||80 - 127||9b) L50 - 10b) R50||loud|
That about wraps up this month's look at sampling techniques. Enjoy, experiment, and happy sampling.
Feature by Tom McLaughlin
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