Reginald Vincent Holmes
... possibly. He did say it, though.
It's definitely not Shakespeare, or if it is him, then it's not anywhere that multiple experts can find. It's also probably not Santayana; people can't find a reference for that either. Well, except this person, who quotes a poem they attribute to Santayana. Only problem is, that poem isn't by Santayana. The verse in question is:
The earth has its music for those who will listen,
Its bright variations forever abound;
With all the wonders that God has bequeathed us,
There is nothing that thrills like the magic of sound.
Which is probably from Holmes. There is, for example, this 2001 newsletter crediting him, and multiple sources point back to the poem "The Magic of Sound" from his book Fireside Fancies. Not having said book or anything but The Internets to go on, I can't be completely sure of this. But it seems more likely than Shakespeare or Santayana, at least.