For the general sense of tone:
* Mood
* Atmosphere
* Feeling
* Style
* Manner
For tone of voice:
* Inflection
* Pitch
* Cadence
* Voice
For tone in writing:
* Style
* Voice
* Attitude
* Perspective
To give you the best synonym, please provide more context about how you are using the word "tone." For example, are you talking about the tone of a conversation, a piece of writing, or a musical performance?