Monday, December 13, 2021

TECHNIQUE: The Art of Sampling. Part Three. Multi-Sampling. Keyboard Mapping.


So in Part Two we learned the basic processes of recording samples and the essential editing procedures of trimming, normalising, reversing and looping. 

In that example we were dealing only with a single sample. 

However, in order to make both acoustic recreations and creative synth type sampling sound authentic and musical we will usually require more than a single sample. 

Playing a single sample across an entire keyboard is not very musical. The different pitches of a sample are achieved by slowing down or speeding up the rate at which the sample is played back. The original sound undergoes major changes when it's pitch is shifted beyond even just a few semi-tones. 

The other reason we need several samples to accurately re-create authentic acoustic sounds lies in the nature of many instruments and sound. If we take a piano as an example and compare, for example, the sound it produces from key C3 and key C4 it is not simply the same sound an octave higher. The sound differs not only in terms of pitch but also in terms of 'timbre', and also possibly level. In other words, C4 isn't just C3 an octave higher, it's a completely different sound. 

To demonstrate this, take a single C3 piano sample and play it across your sampler's keyboard. See how far you can move away from C3 before it stops sounding like a piano!

So to achieve sampled instruments that sound authentic and musical, we need several samples recorded at different pitches which are then 'mapped' across the keyboard. The original 'root' pitch of the sample is at the centre of each sample group. Each group can be described as a 'keygroup' or 'zone'. 

So now each sample only needs to deviate a few semitones from the original before the next sample zone 'takes over' so to speak. If you have the available time, available memory, and a suitable sampler, there's nothing to stop you sampling every note from an instrument and have keygroups consisting of just a single note.  

See the following screenshot from Bitwig's Sampler instrument to illustrate the concept of keyboard mapping. 

Using a sampled piano instrument as an example, you can see the different samples that each note of the keyboard plays. Here, there are 19 zones each with it's own sample with a different sample every perfect fourth (5 semitones). 

Horizontally, you can see the 19 different key zones each with it's own sample, but the actually number of samples is 57, that's because each key zone has 3 samples with a different one sounding depending on how hard a key is played, or at what velocity to use the correct term. This is called velocity mapping and we'll take a look at this in Part Four. 

Keygroup Zone Crossfading. 

Some sample instruments further enhance the concept of keyboard mapping by allowing you to 'crossfade' between groups. Slowly and gradually 'weaving' audio from adjacent groups so the differences between each keygroup sounds less 'defined' and stark. 

So in this post we've seen that to musically recreate acoustic instruments and synthesized sounds we need several samples recorded at different pitches, not just one. 

In the next post we'll discover that often one sample per group is not enough. Instruments also sound completely different depending upon how they are struck, plucked or hit. How loudly an instrument is played can produce completely different timbres. So in Part Four we'll deal with 'velocity' switching and fading. 

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