[MarkK]

Please explain this, as it is not something I've experienced in over
25 years of editing digital audio. There is no amplitude in the
signal at zero-crossing points, so how can it possibly result in a
click?



In theory you have to match not only the amplitudes but also the slopes. If
you butt spliced together 2 sine waves of different frequencies at the zero
crossing you will still get a click because the slopes do not match at the
splice and there will be a discontinuity in the waveform. In fact in
theory you have to match all the derivatives of the two signals to
completely eliminate any click. In other words, for there to be no click,
in theory, the waveform and all it's derivatives have to be continuous.

So the only practical way to do this is to splice two wave forms together
during silence, i.e. not just when the waveform crosses zero, but when it
has been zero for a time and will be zero for a time.

Mark