Definition: Any sound that considered to its quality, pitch, strength, source.
Examples:
My foot fell asleep
right inside of my shoe
from sitting around
having nothing to do.
It hadn't drank warm milk
nor tried to count sheep;
it just wasn't busy,
and fell right asleep.
The poem above has the tone of humour.
Significance: Tone helps poets to express their attitude, emotion or opinion to something or someone which can easily send the message that poet wanted to convey.