Stretching a video clip to bar length couples visual rhythm directly to musical tempo

A core AV coupling technique is to make a video clip’s duration equal to one or more musical bars. When the tempo changes, the clip’s playback speed changes proportionally so the clip always completes in exactly one bar. Visual and sonic events then align at bar boundaries: a clip that builds over four bars peaks with the musical phrase. In CoGe with Ableton Link the video clip stretches to the bar, making CoGe’s video clips roughly analogous to Ableton Live’s audio clips and patterns — the visual analogue of looping audio clips in a Live session.

Examples

In CoGe with Link enabled, set a clip loop length to 1 bar. At 120 BPM the clip plays in 2 seconds; at 130 BPM in about 1.85 seconds. The musical phrasing and visual cycle stay aligned regardless of tempo changes.

Assessment

What happens to a 4-bar video loop when the Ableton Link tempo rises from 120 to 140 BPM? Why is bar-stretch preferable to a fixed-speed clip for live AV performance?