For most people, learning to play music by ear is not an overnight process. It takes regular, dedicated practice and a LOT of motivation. Without a strong reason to keep up your ear training and music theory study, you are not likely to get very far.
So why bother developing your musical ear in the first place? Different people have different reasons, and it's important to know and remember what that reason is for you. Perhaps you'd like to create songs out of the melodies you hear in your head. Or you might want to be able to play along with other musicians who gather for informal jam sessions. Maybe you just want to pass your university course in ear training.
Whatever your motivation, if you have a strong enough reason WHY, you are much more likely to figure out HOW to develop your ear. In addition, by keeping that reason in mind as you practice, you'll find it much easier to continue with your training, even when it feels like you're not making much progress.
Here are some of the benefits that have traditionally motivated musicians to improve their play-by-ear skills: - stronger ability to improvise music - able to play along with songs quickly after hearing them - freedom to express the music they hear in their minds - better able to remember music and anticipate chord changes - able to learn songs and play without sheet music or tablature - bigger musical vocabulary and range of expression - better understanding of how music 'works'.
For me, it was primarily a strong desire to improvise solos on the guitar that drove my ear training practice. At first, I could see absolutely no connection between learning to identify intervals and improvising a guitar solo. Still, I had a strong belief that by developing my ear, I could somehow unlock many of the mysteries of improvisation, and this turned out to be true.
By constantly keeping that reason in mind, I was able to maintain enough motivation to work through a pretty extensive course on relative pitch, which in turn opened the door to a whole new level of musical freedom and discovery. So what is it that makes YOU want to become more of a 'play-by-ear' musician? Know your reason, and you'll find the journey becomes much more enjoyable and rewarding.