I would imagine that with vocal tracks the issue would be more evident than say a finger picked guitar where any gap would be hard to detect. Because there are natural gaps between notes. With vocals especially oohs and aahs there is not a infinite time one can hold that note naturally. So “ooh” duration would be an issue.

If per say one had a series of bars where there was a chord progression, and we wanted a vocal background track of “oohs” to start at the beginning of the measure or bar and end near the end so it sounds more natural, like the singers were taking a breath. What about opening the song up in a full DAW, and lining up each “ooh” to the start of each bar or measure. Then so many tools can come into play. Copy and paste, snap to grid, etc.

Maybe this does not help at all, and it’s just me musings over your issue. Thinking out loud here.

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