So, this is a fairly niche post. Not only are barbershop arrangers a reasonably niche interest group at the best of times, but to talk about one particular type of embellishment, in one particular point of the musical structure, is getting pretty specialised. But this post actually grew out of a conversation with a performer about issues they were having with a particular piece of music, so it matters. If in a rather niche way.*
For those dropping in from other musical traditions: the swipe is what we call it in barbershop where the chord changes within a held syllable. This may entail the lead holding a melody note while the other three parts change notes, or it may involve all four parts changing at once. In the latter case, the lead is often switching role from melodic focus to part of the harmonic background in the process, so these ones require rather more sophistication to bring off.