Crossfading over a couple of waveform cycles hides edits in sustained pitched notes

On a held pitch or repeated pattern the waveform repeats regularly, so placing an edit there and crossfading over one or two complete cycles aligns the waveform phase across the join, giving edits from serviceable to remarkable. It is less reliable where the cycle length changes: notes with vibrato, mid-note tonal change, and vocal diphthong transitions — the author prefers to hide such edits in dull closed-mouth “m”/“n” sounds; sometimes a longer crossfade’s phasey artifact is the lesser evil.

Examples

Editing between two takes of a held violin note is transparent when crossfaded over 2–3 waveform periods; the same cut across a note boundary without crossfade clicks.

Assessment

State the conditions under which a cycle-length crossfade is transparent and two situations where it is unreliable.