Some musicians play with their eyes. My wife has a friend and you can hand her the sheet music to anything and she can play it just like it's written. She can't write a song though. She can't play be ear. But man can she read.

Other musicians play with their ear. They have perfect pitch. They can hear someone play and figure it out real quick and copy it.

Not all players are composers. They play what other people play really well. Composers are the people who come up with music in their head. Several have said they have no idea where it comes from, it just comes. Everyone is trying to find the magical trick to writing great songs but it's a big mystery. Some people have the gift. Others don't.