Musical sound (4)
'musical sound' is the definition.
(I've seen this in another clue)
This is all the 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" .)