This is an interesting link between two geniuses from alternate fields. I guess when you achieve total understanding, the idea of 'pre-existing harmony' is plausible. Here is Einstein's thought of Mozart's musical process,
Music was so pure that it seemed to have been ever-present in the universe, waiting to be discovered by the master.and likewise, a similar discovery of his own physical theories,
The laws of nature, such as those of relativity theory, were waiting to be plucked out of the cosmos by someone with a sympathetic ear.