Written 1998/11/28
If you own a sampler or a wavetable synthesizer, it's just possible that you might come across a sound editing option called sample start modulation, or offset. It may sound all very mysterious and esoteric at first, but this option opens up some interesting possibilities for creating or modifying a sound once you understand it.
Let's suppose you've sampled a voice saying "A B C D E" (or that your wavetable synth has such a sound onboard). Sample start modulation will change the point where the waveform begins playing. With the start value at zero, the sound will begin at "A", at a value of 50%, the sound begins about halfway through "C", et cetera.
But this kind of modulation has far more musical uses than the example above. Imagine now that you have a sample of an instrument with a strong attack. It could be a piano, a resonant synth bass, chiff flute, anything where the sample starts loud or bright, and then fades quickly to a quieter or less bright tone. You access the sample start modulation section of your sampler/synthesizer. By changing the sample start values you will be able to hear the effect it has on your chosen sample. The piano, synth bass, or flute will all grow smoother or more percussive sounding as you change the values.
At this point you may notice an annoying pop that occurs occasionally when the sample start is changed. This is a result of the sample starting at a point of relatively high amplitude in the waveform, which causes something like digital clipping, or distortion. If you're like me and consider this effect undesirable most of the time, here's a simple trick to get rid of those pesky pops. Go to the envelope section that controls amplitude. If you've never been in this part of your keyboard or rack, don't worry, the following should be fairly easy to do. Find a parameter called attack time and set it to its lowest value above zero. What this does is create an ultra-fast fade in at the start of the sample every time it is played, and should take care of that unwanted popping.
Now, assign a modulator for the sample start, the varieties of which may vary from one machine to another. This could be the mod wheel, key velocity, CV pedal, LFO, random or noise modulation, to name some common examples. Make sure though that the one you use doesn't affect another parameter such as LFO depth or volume, which may interefere with the desired effect. With your modulator chosen, put the sample start point back to zero and turn a parameter called modulation amount. This will control how much the modulator changes the sample start point. A value of about 75 to 99% tends to yield the most dramatic results. Now as you turn the mod wheel or hit the keys with varying velocity, the attack of your sound will change in nifty ways as you play. Experiment with different samples, modulators and values. You might even want the sample to start near the end with the modulation amount having a negative value to bring it back towards the beginning. It's all up to you.
Hopefully I have been more helpful than utterly confusing, and you'll be breathing new life into your own samples and/or patches!
