Now we descend to the real situation, in which
the period of the waveform cannot be assumed to be arbitrarily long
and integer-valued. Suppose (for definiteness) we want to
synthesize tones at 440 Hz. (A above middle C), and that we are
using a sample rate of 44100 Hz, so that the period is about 100.25
samples. Theoretically, given a very high sample rate, we would
expect the fiftieth partial to have magnitude 
compared to the fundamental and a frequency about 20 kHz.
If we sample this waveform at the (lower) sample rate of 44100,
then partials in excess of this frequency will be aliased, as
described in Section 3.1.
The relative strength of the folded-over partials will be on the
order of -32 decibels--highly audible. If the fundamental frequency
is raised further, more and louder partials reach the Nyquist
frequency (half the sample rate) and begin to fold over.
Foldover problems are much less pronounced for waveforms with only corners (instead of jumps) because of the faster dropoff of higher partial frequencies; for instance, a triangle wave at 440 Hz. would get twice the dropoff, or -64 decibels. In general, though, waveforms with discontinuities are a better starting point for subtractive synthesis (the most popular classical technique). And furthermore, subtractive filtering will not remove foldover once it is present in an audio signal.