The idea is to learn how to hear the difference between two musical notes in a given key / octave, and be able to identify what that difference is, based on the root note. This is otherwise known as an interval: the space between two notes. For example, a minor 3rd, or a perfect 5th (think the Star Wars theme tune!).
For a great description of what an interval is, click here. I also came across this iTunes U video lesson by Shawn "Thunder" Wallace [iTunes Link] describing the difference between perfect pitch, relative pitch and something that Shawn calls true pitch. Very interesting!
This may sound rather complicated, but really you don't need to know any of the theory when it comes to using the Relative Pitch app. At its simplest, it will help you to hear with more detail what it is that you're listening too
Relative Pitch [iTunes Link] consists of two main modes: training and testing. When you open the app, you kick off with the first lesson (of which there are 14) in the training mode. Once the first lesson is complete, a corresponding test is unlocked to examine what you have learned. On passing that test the next lesson is unlocked, and so forth.
Relative Pitch will teach you to distinguish ascending, descending and harmonic intervals across four octaves. With in-app volume control, in-depth customization of the training mode, and even being able to choose the root note of the octave you want to train from, you'll make strides.
Whether you are a seasoned musician or a complete beginner, Relative Pitch will have you listening with a sharpened ear and a greater appreciation of the music you love.
The Relative Pitch app costs £4.99, but there is a lite free version of the app here [iTunes Link] so you can try it out.
Also, keep an eye out for the revamped Easy Ear Training website launching in the coming weeks.