Referring to pronunciation:
* Dialect
* Brogue (especially for Irish or Scottish accents)
* Drawl (slow and drawn-out speech)
* Inflection (variation in pitch or tone of voice)
* Pronunciation
* Voice (often used figuratively)
* Twang (a nasal or sharp tone)
* Slang (informal language or pronunciation)
* Jargon (specialized vocabulary of a particular group)
Referring to emphasis:
* Stress
* Emphasis
* Highlight
* Focus
* Emphasize (verb)
Other related words:
* Tone
* Cadence
* Rhythm
* Delivery
* Articulation
The best synonym to use will depend on the specific context and the nuance you want to convey.