Multisampling - What is it / How to do it

What is Multisampling
It is commonly known that hardware gear (or real instruments) in most cases, far outperforms the sound quality, depth, and "tweakability" created by software synthesizers (soft-synths).  Therefore, the urge by producers to have analog, real instruments, or other hardware sounds for use in their software production environment to capture that unique sound in a soft-synth environment is common!   In order to properly do this you must step into the world known as Multisampling! 

Multisampling is the process of taking different keys (or pitches) of the same sound from external gear, or instrument for use in a software sampler.  By taking multiple keys (multiple samples) of the instrument, this allows you to map these same keys out to their respective virtual sampler key placement.  Consider it as though you have just taken that instrument, and brought it into a virtual production environment with the ability to play it in different keys.

Note: Throughout the rest of this tutorial, we will only focus on hardware (synthesizer) multisampling, but the same basic rules apply for all instruments.

Recording Multisamples
To record multisamples you obviously need hardware to record from, and a relatively good soundcard with line-in capability.  Most common multisamples are recorded at 44.1kHz / 16 Bit quality WAV or AIFF file type, but this is totally up to you if you want to go with a higher quality.  The downfall to higher quality recordings is your multisample file size will be excessively large, and tends to take more RAM to run.


In most cases, the BEST multisamples to use are ones that have the most key recordings from the gear.  For instance, if you record only one key of every octave from your synthesizer, you are required to map that original recording file across a full octave to fill up the keys you did not record.  This leaves it up to the software to artificially change the key (bend the pitch) of that original sound file to sound appropriate at the respective key.  This results in unwanted irregularities in your multisample when playing the multisample back.  The more keys you record from your hardware, the less noticeable the artificial key change (pitch shift) will be.

Recording Tips
- When recording your original multisamples, (in most cases) turn off all effects that may be running through the synthesizer. (Delay, Reverb, Compression, etc.)  You can always add these later!  Raw (un-effected) samples leave you space for more flexibility and creativity.
- Record all synthesizer samples at highest levels possible without clipping, to improve SNR (Signal to Noise Ratio) levels.
- It is suggested that when recording your original files from hardware that you name the files according to what key they were recorded in, therefore mapping the keys will be easier. Example: Synth101-D#1.wav
- A normal wave editor program (Soundforge, Wavelab, etc) is fine to record everything for multisampling purposes, but it is suggested that you use something with a "recording" step sequencer with your outboard gear, (Cubase, Logic, Sonar, etc) and you can lay out all the multisample keys individually in the sequencer, then record them.  Therefore, in the end they will all be the same length, and all your synthesizer FX envelopes (Sustain and Release in particular) will all be the same for each sample.

In the following visual example I will use the NN-XT found in Propellerhead's Reason simply because it has an intuitive interface for showing an example of Key-mapping.

Mapping Tips
- When mapping samples that must be stretched it is suggested that you expand the mapping out from BOTH SIDES of the Root Key.  Notice in the visual example above that the root key (at D#1) is placed in the center of the "Lo Key / Hi Key" area.  The reason behind this is, if you place the sample at the beginning or end of the key map, you have a longer area to stretch the sample, therefore compromising quality.  With less keys to stretch across, the pitch morphing of the sound isn't as noticeable.  So placing all the root keys in the center of their respective "Lo Key / Hi Key" area saves quality.
- Some programs will automatically map your samples for you.  Check your sampler's documentation on how to do this.  It can save you a LOT of time!
- Notice in the image above that the "Play Mode" is set to "FW-Loop".  This allows the sampler to loop that audio indefinitely, so for as long as you have the keys sequenced for (or controller keyboard keys held), the synthesizer will continue to play looped.  Sometimes the looping doesn't sound right because of natural LFO movements of some synthesizer sounds.  If that is the case, you can try to adjust the "Loop Start" to a different setting in an attempt to get a smoother transition of the loop's recurrence.

One-Shot & FW / BW
If the synthesizer sample is under constant change (Mostly Pads), and never repeats itself it must be considered a one-shot multisample, meaning the sample cannot be looped, or it would sound unnatural if it were looped.  With one-shot samples, you can TRY applying a "Forward / Backward Loop".  What this will do is play the sample forward, then as the sample ends play it in reverse, then back again, etc.

Forward Loop
If the synthesizer sample sustains a common characteristic, you can loop it so the file repeats. 


There are several other less-common types that aren't necessary to mention, but if you would like to learn more about them, consult your samplers manual for Sample Loop Play Modes.