Apple Motion 3 - Manual (Page 507)

Chapter 6 Keyframes and Curves 507
When keyframing (Record) is enabled, the changes that you apply to the object are
applied at the current playhead position (viewable in the mini-Timeline at the bottom
of the Canvas). A keyframe is automatically added (though no indicator appears). If you
move the playhead to a new position and change the shape or position of the object,
you create a new keyframe. Motion automatically figures out the shape and position of
the object during the frames between the two keyframes you set.
Important: When Record is enabled, a red keyframe appears in the center of the
selected object. When moving the object in the Canvas, do not click the keyframe in
the center of the object as you are actually selecting and repositioning that keyframe
instead of the object’s current position.
To scale an object over time using the Record button:
1 Click the Record button (or press A) to turn on keyframe recording.
You can also choose Mark > Record Animation.
2 Select an object in the Canvas.
3 Move the playhead to a new time position.
4 Resize the object by dragging a scale handle.
5 Click the Record button (or press A again) to turn off keyframe recording.
The object is scaled over the interval you set. In this same way, you can keyframe any of
the transformation parameters for your object.