One of the basic dialogue tags is said (he said, she said, they said). Now, some people are of the opinion that the most evil thing you can do is overuse said (here, here). But others are equally adamant that said is the best way to write dialogue (here, here, here, and here).
You might be tempted to use an alternatives to said and pick spoke. This would seem to make sense: they both refer to using one's vocal cords to impart sound. It's talking, right? But it's not a blanket alternative.
Let's use an example. I'm not a writer by profession, so bear with my examples (this is what my brain thinks about at three thirty in the morning and I'm wide awake).
He said, "I am not going to eat that slop."
"It's not for you anyways," she said, trying to hide the hurt in her voice. "Melvin is coming over for dinner."
"Poor fool," he said under his breath.
Here is what we'll call the traditional method of writing dialogue. Simple and easy to follow. Note the punctuation: comma before the opening quotation mark in Sentence 1; comma between the end of the spoken words and ending quotation mark in Sentence 2 and Sentence 3.
He spoke, "I am not going to eat that slop."
"It's not for you anyways," she spoke, trying to hide the hurt in her voice. "Melvin is coming over for dinner."
"Poor fool," he spoke under his breath.
This is the same as Option 1, but I replaced said with spoke (no punctuation changes). This is incorrect and should NOT be in your manuscript.
He spoke slowly, sending bullets to her heart with each word. "I am not going to eat that slop."
"It's not for you anyways." She spoke defiantly, trying to hide the hurt in her voice. "Melvin is coming over for dinner."
"Poor fool." He spoke under his breath to avoid any more hysterics.
Notice that in Option 3, spoke isn't involved in the actual dialogue. It's part of a dialogue beat, not a dialogue tag. And the punctuation has changed as well, because spoke is in its own sentence.
Looking in the dictionary, the word say has a past tense of said, a past participle of said, a present participle of saying, a present first singular of say, a present second singular of say, and a third singular of says. Nowhere does it list spoke as a part of say's tenses.
And likewise, in looking at speak, it lists spoke, spoken, speaking, and speaks. Nowhere does it list say as part of speak's tenses.
So please, be careful how you use spoke in your manuscripts.
I have spoken.