Tone is established almost immediately and is expensive to change later. An audience decides in the first few seconds whether a piece is serious, ironic, warm or cold, and everything subsequent is interpreted through that decision. A joke arriving in minute three of something that established itself as sincere does not read as funny; it reads as a mistake.
The most common commercial failure is tonal inconsistency introduced by committee, where each stakeholder’s note pushes the piece a little further from wherever it started. The result is a piece that is not confusing in any particular moment and is unaccountably difficult to watch.
It is distinct from mood, which varies scene to scene, and from voice, which belongs to a speaker. A piece can move through many moods while holding one tone, and it usually should.
What is tone in a film or video?
The attitude the piece takes towards its material. It is set within seconds, and everything after it is interpreted through that setting, which is why late tonal shifts read as errors rather than as variety.
What is the difference between tone and mood?
Tone belongs to the whole piece and should be consistent. Mood belongs to a scene and should vary. A piece can move through many moods while holding one tone.