I've read a text aboat early friendship effect on relationship with siblings. This text is in the book 'Vocabulary for IELTS'. In a sentence it says:
And children who as preschoolers were able to coordinate play with a friend, manage conflicts and keep an interaction positive in tone were most likely as teenagers to avoid the negative sibling interaction that can sometimes launch children on a path of antisocial behavior.
I couldn't find 'in tone' anywhere on the Internet!! What that means here?!