Layering Sound (Part 4)
Multi-sampling & Overdubbing
Keyboard programmer Paul Wiffen draws to a close his popular series on the merits of sampling techniques with a close look at two means of extending your sample playback range.
If you have been following our series on sound sampling, you will have discovered by now that, however good a sample may sound when replayed at the sampled pitch, there are few sounds which are usable when the pitch is shifted up or down more than an octave. This month session programmer Paul Wiffen concludes the series with an investigation into two ways of overcoming the problem.
The first thing you should understand is that this problem with samples replayed much faster or slower than the original sampled rate is not a drawback of any particular instrument. It is a characteristic of sound itself. Remember Pinky and Perky or Bowie's 'Laughing Gnome'? Those voices were created by playing normal speech recorded on tape back at double speed. The human voice is perhaps the most vulnerable of all sounds to pitch changes. Move the pitch up more than a tone and it already starts to sound strange- hence the runaway success of harmonising devices in recording studios.
Having said this, most samplers these days provide facilities which allow you to get around the problem. The Akai S612 rack-mount sampler does this rather cleverly by providing an overdub facility which allows you to cheat(!). Of course, it tells you nothing of such things in the owner's manual. Deciding what to do with this facility is left up to you. Of course, you can mix two completely different sounds together, but the most conventionally musical use is to achieve a wider, more useful pitch range on one instrument.
The best example of this is on a piano sound. A single piano sample is only really useful played back within the octave in which it is sampled. However, by using the following procedure you can get a result which is pretty authentic over five octaves or more.
1 Start by sampling Middle C or a note nearby - it often pays to play around with various different notes on a piano to find the one that sounds best. Having executed your sample as well as our previous instalments should have taught you, save it to disk. You should make sure that you do this before proceeding to the next stage as an unfortunate move can lose your original sample. Take that disk out and insert another.
2 Now overdub the note an octave higher than your original pitch. If the balance is even between the two notes (unlikely but possible) then save it straight away. If not, then load the original sample again. If the old sound was too loud, then turn up the Record level. Conversely, if the new sound was the stronger, you will need to turn Record level down. Re-sample the higher pitch. Whenever your mix comes out evenly balanced, then you should save it on a new disk. Try playing the mixed sample now. You should find that it works over a larger range.
3 If the sample range is still not enough for your purposes, there are two further options open to you:
(a) You can repeat step two again to add a third sample, either an octave below Middle C or two octaves above, depending on where you need the extra range. There is no end to the number of times you can repeat this stage (well, at least not until you run out of octaves to sample). Obviously, achieving a reasonable volume balance between eight samples is very tricky, especially when you can only control the volume of the most recent, and all those octaves together will make you sound a bit like Liberace!
(b) The second alternative is to go back to your original sample and overdub the sound two octaves below or above directly onto it. Obviously, this will give you a more widely-spaced sound, but one which can be played realistically over a greater range.
This procedure is a little hit-and-miss by nature and there is no real way to know in advance whether 3(a) or 3(b) will give you the best result for that particular instrument. It can be quite fun though, and you may well come across some interesting side-products along the way, which are perfectly usable in their own right. Don't forget to save the result at every stage though, as once you have overdubbed a new sample you can't even change its level, let alone get rid of it.
With this more expensive option (currently available only from the £1300 plus machines instead of the less than a grand variety), hindsight is possible. Now you can make samples and place them across a keyboard as required. This is the best procedure to adopt:
1 Sample at the top of the range of your target instrument first. This is necessary because on most instruments the top sounds last the least amount of time. This means that you can make sure that any spare memory left afterwards can be used to capture as much of the longer duration lower pitches as possible. If your sampler can use various sample rates, then I suggest you use a higher rate for the upper notes, to make sure you don't lose the top end of the higher harmonics of what are already high fundamental frequencies. The Prophet 2000 excels at this.
2 Loop as early in the sound as possible as this will save valuable memory. The biggest disadvantage with multi-sampling is that available memory disappears into thin air, it seems, when you use multi-samples. Unfortunately, the mapping system offered by each multi-sampling keyboard on the market is totally different for each machine, so there are no real hints to give you here, except read the manual and experiment.
However, there are visual editing systems that work with the Apple Mac coming shortly for both Sequential's Prophet 2000 and the Ensoniq Mirage. Watch this space for a future issue where we check them out. In the meantime, that wraps up our present series on the merits and applications of good sampling techniques. Hope you've found it useful.
If you have any queries raised by any part of this sampling series, then don't hesitate to write to us at the editorial offices (address on page 2) and we'll endeavour to resolve them for you.
Feature by Paul Wiffen
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