Who said, "The music is not in the notes, but in the silence between"?
It was Wolfgang Amadeus Mozart (1756 - 1791) who talked about the space in between the notes. He said: "The music is not in the notes, but in the silence between." All experts tell us that the guy knew what he was talking about. It is also clear that other great musicians by the way they composed music know this, whether they expressed it verbally or not. Great artists like Miles Davis and Bob Dylan said that they had Mozart's idea in their heads when they were recording or just drafting songs.
True experts will try to point out what exactly goes on in between the notes. It's not always a literal silence. It's believed that each note is usually still ringing out before the next one is played. Something real is happening that relates to silence. Those who compose and know about elements of music are listening to the silence.
This is part of what Mozart may have been trying to convey with this somewhat nebulous "space in between the notes" statement. It's something that all good improvisers or composers know. They write or play a note, and then the next one will come from the silence. This will happen, however, only if one is listening for it. Otherwise, the sounds and notes (experts say they hear) are a stream of run-on sentences that have no meaning. No subtlety. No breath.
Mozart wanted music lovers to become aware of the silence between the notes. He asked them to listen to the silence in his music. They would then hear all the notes appear as they heard his music.