In point of fact, the number of the
most recent value chosen is kept in a register known as the phase
accumulator, which has more precison than neccessary to handle the size
table used. The high part of the p.a. points into the table, and the low bits
contain the fraction. The sampling increment is added to the phase accumulator
during each iteration, which will produce the appropriate stepping action.
Digitally speaking, the value obtained from one wavetable
lookup is added to the sampling increment for another wavetable lookup.
The carrier is the oscillator we listen to; the
modulator is an oscillator that changes the frequency of the carrier at
an audio rate.