Jonas experienced seeing-beyond. What did Giver experience?

From the text:

"When I was just a boy, younger than you, it began to come to me. But it wasn't the seeing-beyond for me. It was different. For me, it was hearing-beyond."

Jonas frowned, trying to figure that out. "What did you hear?" he asked.

"Music," The Giver said, smiling. "I began to hear something truly remarkable, and it is called music. I'll give you some before I go."