High level ear training was one of the most difficult, yet productive endeavors I perused while in college. While as a youngster starting with the guitar, I did develop my ear a great deal, but wish that I had had some structure and not only had an idea in my head, but a symbol to put on paper. While music is a perception it is very useful to be able to relate your perception to other people, and their ideas.
Ear training is the key to a true understanding of the musical language, and the ability to speak it.
You can start training for free at: teoria.com, more resources to come.