An acronym for trombones and baritones. Often used to refer to the low brass section for when things need fixed or sectional. Also slang for refering to others in their section. Usually used when the trombones and baritones are so much alike you can't tell who really goes in which section so they just combine them together to make it easier for everyone.
"Bones and tones, run that last measure and don't mess up that hight A"
Person A:"What section are you in?"
Person B:"The bones and tones of course."