Developing your aural (hearing) skills is important in music creation. You can develop many new skills that include the ability to improvise on your instrument - straight from your mind, name tones and chords by ear, transcribe a tune when you hear it and learn and recall new songs by ear.
As the drummer for my band, The Upper Room, I know the importance of a "musical ear", especially when it comes to performing live in front of all kinds of audiences and at different types of venues. Music is really all about hearing! Good musicians have an internal sense of pitch, rhythm, dynamics, etc., and use their ears to recognize notes, intervals, chords, major/minor tonality, scales, seventh chords, dominants, and so forth.
A musical ear is the single most important skill for musicians, but most musicians have poor aural skills because they do not practice ear training. Does your ear perceive the difference between, for example, major and minor scales? Between a 4th and a 5th? Or between a mi7(b5) and a dim7 chord?
It can be very frustrating. You can hear a piece of music just fine in your head - but when you try to play it, it just doesnï¿½t come out right. This is an example of what ear training can help you to improve. Ear training will help you to:
Play the music you intend to play.
Understand the music you hear.
Hear the music "in your head" when you read it.
Bring together sight and sound.
Ear training will help you develop greater musicality, confidence and enjoyment of music. A better ear will help you when you play music, sing, improvise, compose and transcribe. Ear training will give you a better understanding of all the things you are doing with music. You will notice things you did not hear before, and your errors will become easier to detect, so that you can correct them and learn from them.
Here are some links that I found helpful in developing my musical ear:
http://www.good-ear.com - The Online, Free Ear Training on the Net
http://www.earmaster.com - EarMaster Pro is a great tool for training your ear