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Map Rap

Turning a collection of samples into a usable keyboard patch is one of the most important aspects of sampling. Tom McLaughlin puts samples on the map.

Multi-sampling and keyboard mapping are two of the most important aspects of producing a good sample. But what are they and how do you perform them?

IN A NUTSHELL, mapping is where all your hard sampling work comes together. A map may be as simple as one sample on the left-hand side of your keyboard and another on the right, or as complicated as every note of an instrument being laid out across a keyboard, spanning its entire musical range in semitone steps. A keyboard map may take into account loud and soft versions of a sound, and in the case of multisampled instruments, positional crossfading of samples from one map member to another.

There is a slight difference between a keyboard map and a multisample. All multisamples are maps, but not all maps will be multisamples. Confused? See if this helps.

Mapping is the assignment of any two or more samples to different keyboard zones. The samples may or may not be related to one another.

Multi-sampling is the assignment of two or more samples to various zones of a keyboard in such a manner as to simulate an instrument's or group of instruments' natural transition of tone colour, and/or characteristics from one range of pitches to another.

And then there's multi-mapping: a keyboard layout that contains different "instruments" or zones, any of which may be single samples and/or instrument multisamples. Typically, one would have several "instruments" overlapping one another on the keyboard in a multi-map, each accessed by a different MIDI channel.

While sampling every nuance of an acoustic instrument is beyond the capabilities of most samplers, capturing a realistic playing style and character in a multisample across your keyboard is possible with many, if not most samplers. And a realistic multisampled map is not that difficult to construct.

The skills are those of wise use of storage space, judicious looping, making the most of your sampler's facilities and lots of loading, editing and storing of sample material. A realistic multisample map is not for the faint hearted - this is a time- and labour-consuming business. From start of sampling to completed map will take you the good part of a weekend at a comfortable pace, giving a very professional-sounding set of samples at the end of the day.

Source Material

SOURCE MATERIAL IS vitally important. Your mapped instrument can be no better than your source recordings. For the best results, get a hold of, or make a recording of, an instrument's entire chromatic range. You can work with recordings or sampling tapes with small intervals between their notes (2nds, 3rds, 4ths), but you'll be severely limiting your choices of map members. I mean, if you're going to go through all this, you might as well go for gold. You'll be glad you went out of your way...

Excluding keyboards, acoustic instruments generally have a usable playing range of almost three octaves - typically 32-34-notes. Physical limitations seem to prevent wider ranges. Some instruments can produce harmonics, further extending their range to around five octaves at the most. Here we'll be concentrating on an instrument's "normal" playing range of about thirty-odd notes.

We'll be working with sound material that can have its sustain portion typified, in terms of sampling, with a reasonably short loop. Sounds that reach a steady tone early on in their duration allow the greatest scope for creative mapping - they enable you to include more samples in your map, giving a smoother transition between registers.

Solo instruments, such as brass and woodwind, lend themselves well to shortish loops. Some percussive sounds also fall into this category, such as vibes, marimba, glockenspiel, compressed guitar/bass and electric piano. Bowed, plucked and struck strings, vocal and ensemble sounds are more complex, requiring longer loops and another approach to mapping than we're dealing with here.

With many samples spread across the keyboard, a variety of attacks and smooth tone colour transition through the instrument's range more than makes up for a short loop's static tone colour. Besides, short loops (one to several wave cycles long, with or without loop crossfading) take relatively little time to carry out, and there are means of manipulation to conceal or mask the monotony of short loops, as we'll discuss later on.

Floppy disks

BEFORE YOU START you'll need plenty of formatted floppy disks. Even though you want to end up with your "instrument" on one or maybe two disks, you'll need to sample notes across its entire range to start out with, and whittle the number and lengths of samples down to all fit into your sampler. It's so much hassle to have to stop in the middle of sampling to make room for more material, or format a disk, when things are running smoothly.

How much memory does your sampler have and how can it be used? How many samples can be held in memory and used in a keyboard map? Eight, 16, 32, more? This is where all the planning begins: finding out how you can divide your sampler's memory up to accommodate the "ideal" length sample for your map. Although your final samples will probably end up shorter or longer, this ideal length is a good starting point.

For our discussion, we'll be working with an oboe recording in semitone steps, playing medium loudness, sampling into an Akai S900 at the full 16kHz bandwidth. We can have up to 32 samples resident in memory at the same time, and the same number of map members (or Key Groups, as Akai call them). The maximum recording time of 11.878 secs at 16kHz playback will be somewhat shorter with the memory for the keyboard map taken into consideration - samples and maps often share the same memory space.

To be on the safe side, we'll count on having exactly 11 seconds available for sample material. Those of you with other samplers will need to adjust sample rates, times and map numbers according to the capabilities of your unit, but the principles remain the same. You'll find sounds, the nature of which we're dealing with here, take somewhere between ½-1½ seconds to reach a steady musical tone that can be looped. With 11 seconds available in the S900, simple maths tells me that I can have 22, maybe 23, edited and looped ½-second samples resident in memory to construct a map from. More than enough. That's about 2/3 of an acoustic instrument's possible playing range. Even if I can only find 15 fairly evenly-spaced pitches there's still every chance that a realistic map can be preserved on a disk for future use.

Rough Samples

I'VE APPROACHED SAMPLING semitone instrument recordings in two ways. At the present moment in time I prefer the second. The first involves taking a rough sample, maybe two seconds in length of each pitch, naming and saving them as you go. The second uses "blocks" of semitone samples - fill up the sampler's memory, save each "block" to disk, then go back and edit, name and save individual samples as 2-second blocks.

Either way, in the event of more than one recording of a pitch that you can't make your mind up over, just sample and label them 29A, 29B (or if you know the pitch: A, 3A, 3B) and come back to them when matching tone colours and performances.

With some oboe recordings I was working on I found that two-second samples of its 33 notes numbered 01-33 fit onto seven floppy disks in their rough state. From there on the story goes like this...

"If we reassign all key groups three or four notes higher, we'll have a tight map which is more cutting and punchy than a 'normal' key assignment."

Step 1. Discard bad notes. Notes 01 and 04 were pretty questionable. Some were a little sharp or flat, but nothing that couldn't be fixed with fine-tuning.

Step 2. List samples.

Step 3. Trimming. Edit beginnings of samples to leave a clean attack, and save over old file. While you're doing this, start examining each sample, by ear, for tone colour, character and attack quality. Play around on the keyboard with each sample as you edit the beginning to get to know it better. Make a note on your list of samples you like.

Step 4. Assessment. Go through your rough edited samples, keep an ear out for samples that fit into different categories - normal/pronounced attacks, bright, soft, nasal tone colours, for instance. You'll probably find at least two distinct map ideas within a chromatic recording of an acoustic instrument's range. A prime example of this is brass and wind instruments which produce their sound by vibrating air through a tube (of one sort or another) and rely upon divisions of this tube's length and/or varying the vibratory rate with the lips or mouth to derive different pitches. Some pitches are more in tune with the tube's resonant frequency, and these sound sweeter than the rest (with a C flute you'll find the C major scale sounds clearer than the sharp and flat notes). Accomplished players will have spent much time evening out the tone colour throughout their instrument's note span.

The main thing to listen for is the samples that stand out as being more "present" than others. These are the prime contenders for your instrument map. Once you've been through all the samples, assessing them for inclusion in your map, go back and concentrate on the better sounding of the bunch.

If these all fit into your sampler as they are, you might want to try mapping them to your keyboard. Who knows, you may have enough material to build a map from.

Step 5. Trimming and looping. The odds are that you won't have enough "nice" samples to construct a map from, and even if you did there would probably not be enough working memory in your sampler to store them all in one go. This is where trimming their length down and looping samples comes in. With looping, you probably don't need anything like the two seconds of time we've sampled of each note. With my oboe, I found perfectly usable loop material within the first half second of most samples, some had good loops to be found in less than ½ a second, and two needed a bit more than ¾ of a second to settle down to an even sustain.

The reason we've sampled a greater length than we'll most likely need is threefold. First, you may need the length - finding a good tone colour to loop around might not be possible early on. A sonorous tone loop can, if you really need and want to, be moved from the end of a sample and pasted or cross-faded through earlier sample material to get the best of both worlds - short sample with desired tone loop. Finally, some loop crossfade software requires material both before and after the loop to derive its data from.

See if you can at least chop each sample in half, placing a rough (but glitch-free if possible) loop somewhere in there for the time being. Leave problem loops alone for now, coming back to these later on.

Step 6. Rough mapping and rough tuning. With their lengths drastically chopped down and looped, samples are now ready to be rough mapped. At this stage you should be able to fit a goodly amount of samples onto one disk. But before we start assigning samples to notes of a keyboard, we need to tune them to a common pitch. All you need to do is tune one sample, since we numbered each semitone, and adjust the others to that - plus or minus the appropriate amount of semitones as related to their numbers. Don't worry too much about tuning at this stage.

Name sample notes: the key to mapping is not to start with samples from the bottom of the keyboard up, or from the top down, but to begin the process by assigning your favourite samples to their respective notes on the keyboard.

With your best samples playing only their proper pitches, make a mental note of your favourite ones. These are the samples that all the rest (if you need to add more) will be judged by. Simple on or off amplifier envelopes will do us for now.

Step 7. Saving. Save this map as it is, along with its member samples, to a separate disk, your map disk.

Step 8. Filling in the gaps. Go back to your sampler's map page, extend each sample's playback range on the keyboard halfway up and down from its sampled pitch to meet its neighbouring sample. See how that sounds to your ears.

Start experimenting with inserting samples from your collection between map members, especially those with large gaps or greatly differing tone colours. Replace any samples that stick out like sore thumbs and map accordingly. If you didn't before, you should start to hear a certain characteristic unity between samples as you play through the instrument's range now.

There may come a point when you need to insert just one or two more map members, but have run out of space in your sampler. You'll have to start playing the "memory-saving game" in which each sample is examined in minute detail to see if any data can be nibbled off the end. A little bit here, a little bit there... With 15 or so samples already in memory, the "bits" may just add up to another sample. If you still need more space, see if some loops can't be moved forward without losing the essence of the sound, then discard the redundant material.

When you're satisfied, save what you've got, along with any new samples, as your new map.

Take a breather - you deserve it. But don't pat yourself on the back too soon, we're not finished yet. There's a lot of fine tuning to be done.

"In the 'memory-saving game' each sample is examined in minute detail to see if any data can be nibbled off the end - the 'bits' may just add up to another sample."

Step 9. Fine tuning. The first and easiest bit of fine tuning is your samples' relative volumes. With velocity and aftertouch turned off, go through your map and ensure there is smooth flow of levels from one end of the keyboard to the other. Depending upon the instrument, you may want the top, bottom, or a specific register to be louder. This mapping trick can be accomplished here by simulating a loudness curve kind of like DX synths' keyboard scaling.

Exactly the same thing goes for adjusting the filter cutoff point of samples. Some will still stick out more than others due to their brightness. Again, with all possible modulators turned off, go through the keyboard and fine-tune the samples' brightness.

Like the loudness curve, the filter cutoff points of samples can be adjusted across the keyboard to simulate, reinforce or tone down instrument resonance.

Get the old tuner out, go through the lot, get each sample in tune, and you're nearly there.

You can further bridge the gap between neighbouring map members' tone colours by moving their loops. Remember we're working with fairly small loops. These can more likely than not be moved to another position within the sample that gives a loop (you may have to re-adjust length) with a different tone colour - a tone colour that may sound more like what you need to "plug up a hole" in your map.)

Envelopes and Modulation

YOUR MAP WILL benefit greatly from mimicking the loudness and brightness curves of your sampled instrument with your sampler's digitally-controlled amplifier and filter. If your sampler has the provision, a "copy envelope" facility saves a lot of time here. Without explaining all the ins and outs of VCA and DCA envelopes, I urge you to bear in mind that you can soften or bring out the attacks of sample entries to more closely match the rest of your set. Having the DCF decrease its cutoff a little while samples are in their loop will help your short loops somewhat too. Remember, your release time is your ambience control.

A little bit of pitch mod helps relieve the tedium of listening to short loops and gives character and warmth to sustained sounds. Even sounds that in real life don't have a natural vibrato, can benefit from just a touch of delayed pitch modulation. If you have amplitude modulation onboard, try using it to add another element of movement to samples - especially flute, vibes and electric piano.

With their character and place within your palette of sounds in mind, keep track of the modulation rates of different instrument maps and adjust them to suit their respective ranges to add depth and perspective to your mixes. Giving high instruments a faster mod rate than lower ones will help carve a notch out for them to "sit" comfortably in an ensemble situation.

Do a final adjustment to each map member's level, filter and envelopes to make this as smooth as possible and store the lot to disk.

Loosening Up

CONGRATULATIONS. IF YOU'VE followed these instructions you will have in your possession an instrument captured in your sampler that rivals just about anything available from any sample library.

If not, you probably need to replace map members or maybe even the source recordings you used in the first place. Even if this is the case, you've gone through all the motions involved in multisample mapping, and will have a better feel and ear for what's involved the next time around.

You now have a map with samples that extend about halfway from their original pitches to neighbouring samples. If the distances between samples are not too great, this will imitate the character of the instrument with a fair amount of realism. This is what I like to think of as a "normal" map - the assignment of samples to keys following their natural occurrence on the instrument. Let me introduce you to a concept of mapping: "loose", "normal" and "tight" maps.

Using the same set of samples, you can quite easily end up with two distinct remappings which, when overdubbed onto tape, give the impression of three different instruments or musicians playing.

I'll let you in on one of the most basic and useful recording tricks with recording tapes - if you want an instrument to sound brighter and more punchy than it ordinarily would, simply record the part transposed down a whole tone or so with the tape slowed to match. On some old '70s tracks, like those by Earth Wind and Fire, brass parts would be scored a minor third lower than their desired pitch. This not only made them brighter when played back at the correct speed, but makes playing very high notes much easier.

Our samplers are effectively a varispeed tape player. If we take our normal map, and reassign all key groups to three or four notes higher, we'll have what I call a "tight" map - more cutting and punchy than a "normal" key assignment.

Conversely, if we take all our map members and lower their key assignment by three or four semitones, the effect on sample playback will result in a mellower, more laid-back performance - a "loose" map. This is a good method of making polite instruments more poppy or giving a more individual character to two or three of the same instrument overdubbed with itself.

An easy way around finding bright samples to switch to in a velocity-switching map is to layer a tight map under a loose map of the same samples, the tight map programmed to come through once a high playing velocity setting is reached.

The same goes for creating an ensemble with layered maps - placing loose, normal and/or tight maps over each other will produce much fatter sound than more of the same, and will give you fewer problems with phasing. Different envelope shapes and vibrato rates will fatten things up even more.

I'm going to get back to my oboe map if you don't mind. It's nearly there, just needs a few more intermediate samples to bridge a few gaps. Ssshhh - I'm listening for the elusive tone colour...

Previous Article in this issue

Synclavier On The Stage

Next article in this issue

Digigram Studio 24 & Big Band

Music Technology - Copyright: Music Maker Publications (UK), Future Publishing.


Music Technology - Nov 1988



Feature by Tom McLaughlin

Previous article in this issue:

> Synclavier On The Stage

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