Musical sound (4)
'musical sound' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tone that I've seen before include "Shade" , "Bodily firmness" , "Musical note; general character" , "A pitch of note" , "Theobald Wolf . . . ." .)
(Other definitions for note that I've seen before include "mention" , "Consequence" , "Tenner, for example" , "Characteristic" , "Tone of brief written record" .)
(Other definitions for chord that I've seen before include "Group of notes in harmony" , "Combination of musical notes" , "'The Lost - - ' (Sullivan)" , "Group of musical notes" , "Combination of notes sounded in harmony" .)