Timeline Control
Each Viewer is connected to a Timeline that controls playback and current frame.
Autograph lets you create as many Viewer and Timeline panels as needed. Each Timeline can be assigned to multiple Viewers.
Each Timeline has independent playback: multiple Timelines can play back simultaneously yet individually.
In the example above, each composition has its own Timeline and its own Viewer.
When pressing the spacebar, you will only start/stop playback for the Viewer/Timeline under the mouse cursor.
Timeline for other sources
Since the Viewer can display compositions as well as footage from the Project Panel, in this case there's no associated Timeline panel. Instead, the Viewer has a mini timeline to control the playhead and playback for this footage.
Note
The mini timeline can be toggled by clicking on the stopwatch icon in the playback toolbar.