Hiya!
OK, so when you sample something, you're basically storing a very blocky picture of it. The higher the sample rate, the smoother the picture, the lower the rate, the blockier the picture.
As a separate thing entirely, bear in mind that any given waveform can be said to be made up of lots of sine waves at different frequencies. So, for instance, a 6kHz triangle wave consists of a 6kHz sine wave, a 18kHz sine wave, a 30kHz sine wave, and so on. The higher the sine wave frequency, the quieter it is, but they're there.
The sample rate you're recording at, how blocky or smooth the representation of the sound is, should be double the speed of the *fastest* sine wave you want to hear. The more of them you capture, the more accurate the sound.
But you don't really need to know all that, I'm just trying to explain what the "should be at least twice the frequency" bit means. It's NOT twice the frequency of the note, but twice the frequency of the fastest harmonic in that sound that you want to hear.
If you want to know all about sampling, check out these articles:
http://www.soundonsound.com/sos/aug00/articles/synthsec.htm
http://www.soundonsound.com/sos/sep00/articles/synthsec.htm
Basically, in order to get the best sound possible, you want to record a really low frequency sound at a really high frequency sample rate.
As far as wavetable synthesis goes, however (such as the other feature of the A-112 module), you don't need to manually sample this from another synth. It's far easier (to certain geeky types of people, anyway, heh) to make these sounds from scratch on a computer, without them existing as sound until you've copied it across to the A-112 and played it.
I happen to have bought an A-112 module the other month, so I'll look into making some handy wavetable .syx files for everyone in a little while.
With wavetable synthesis, if you were to record an oscillator, it would have to be at an exact frequency that matches the frequency the A-112 is recording at, as you need to use exactly 256 samples to store each and every cycle of the waveform. This would be nigh on impossible to get just right, hence making the waveforms digitally on a computer and copying them across.
But really, as a musician, you don't need to know all this. All you need to know is that if you play a lower note into the sampler, or you sample at a higher sample frequency, the result will sound better.
Does that help at all
Thanks,
Zoë.