Tone and voice go hand in hand in my mind.
The way a book sounds, its rhythm and vibe as the reader turns the pages and reads each sentence. A great voice is smooth like jazz, pushing the reader ahead more than even the action.
Robert Parker is smooth jazz. He can say in 3 words what it might take someone else ten pages to say. He can zing you with a one liner, only to pull it back with a tight emotion in the span of two paragraphs.
Elmore Leonard is jazz as well. More rat-a-tat. Descriptions through dialogue, quick bursts of action, and a subtle characterization built with few powerful words.
I love voice. I love trying to make my work seem effortless and easy. Cutting, adding--a lot of that is plot stuff. But voice... voice has to be natural. You have to know the way you sound and keep it consistent. Whether it's funny, or hardboiled, or sappy... all of that is yours.
Be who you are.
Let your voice shine. The rest will follow.