Arranging : Time, Tempo, Meter, Key, and Chords : Tempo : Tempo and Automation Drift

Tempo and Automation Drift
(With Sample-Based Clips on Tick-Based Tracks Only)
When a track is sample-based, the track’s automation playlist is unaffected by changes in tempo. This means that automation is always aligned with any sample-based audio on the track with sample accuracy.
When a track is tick-based, the automation breakpoints change to match the changes in tempo.
Generally, when applying tempo changes with tick-based MIDI and Elastic Audio, this is desirable. In fact, you will probably want to set all of the tracks in your session that contain automation to tick-based. This way any tempo changes affect all tick-based track automation and track material equally. However, when working with sample-based (non-Elastic) audio on tick-based tracks, tempo changes affect the start location of audio clips, but not their duration.
Since the length of each sample-based audio clip in a track is unaffected by changes in tempo, existing automation data is not aligned with the audio after a tempo change is made to a tick-based audio track.
Minimizing Automation Drift
In general, automation drift is more pronounced with larger sample-based audio clips. By creating many small clips, the effects of automation drift can be minimized, because the start points of each subsequent clip changes as the tempo changes. When tempo is decreased, automation expands. When tempo is increased, automation contracts.
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To break an audio clip into smaller clips, use Beat Detective. For more information, see Beat Detective.
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You can also separate clips at transients or based on the current grid resolution. For more information, see Separate Commands