One reader finds you still can’t do everything with samplers. “Why do guitar samples sound tinny in the higher registers? I’ve worked with several guitar sample libraries and as good as they sound in the first octave or two, above a certain pitch they sound like cheap imitations of some obscure Asian stringed instrument.”
The phenomenon you speak of is not really unique to guitar samples, though it is more obvious on them than most things. When you sing (or play guitar) at different pitches the formants that make up many of the characteristics of the sound do not change in pitch. When audio samples (recordings) get transposed or stretched to a higher pitch (as often happens in samplers) the formants that make up the sounds get pitched up as well. This is the main thing that causes them to take on a fake quality. With distorted guitar samples the problem is even more apparent because now you are transposing the distortion along with the guitar sound, which is not what happens in real life and why most players run clean guitar samples through a distortion unit. Many of the more sophisticated harmony units and audio transposition programs now include algorithms to address what is happening to formants, and this does help the problem in those applications, but samplers do not yet have similar features to act on samples in real time (hello manufacturers – good idea here). Consequently the only way to get around this problem is to record samples across the full range of the instrument. And of course if the instrument in question has many dynamics or variations in its sound then that means mutiplicatively more samples because you have to do several variations of each note. This can eat up tons of RAM (hundreds of megabytes). Most sound design work is an exercise in compromises where an engineer has to find a very delicate balance between the size (and cost) of a sample, how many people it will be applicable to, and the depth of detail and accuracy of it. As RAM continues to go down in price (and samplers can hold more of it) it is likely that the depth of detail in sample libraries will increase.
The bottom line is that in many applications there is still no substitute for the real thing, whether it is guitars, saxophones, or a piano. Samplers are great tools and the sounds they offer are truly amazing in their realism and flexibility, but they still aren’t going to sound completely like the real thing. Remember that samplers are a product category that is only about 15 years old. Consider where the technology was 8 years ago (at half its age) and you may be able to get a glimpse of how far we’ll progress in the next five years. Hang in there.