He spoke, not speaked.
In a neutral voice means without agitation, excitement, or apparent distress.
Matter of factly is almost the same, but suggests further that he did not embellish the event with extra details or interpretation.
"The president is dead. He died at 3 PM of a heart attack." is matter-of-fact. If you can say that without a suggestion of sadness, terror, delight ... then you are speaking neutrally. If you further embellish it to discuss what this may mean to the stability of the government, you are no longer remaining matter-of-fact.