From “The Essential Secrets of Songwriting” website:
You’ve probably seen the ads in magazines and newspapers that promise to help you develop perfect pitch. They’re talking about the ability to identify a note just by listening to it. Most musicians don’t have this skill, and the real question is, how important is it?
It’s not, and you’d be well advised, in my opinion, to save your money. An advertisement I recently saw charged hundreds of dollars for a CD program that promised to teach this ability. Save your money; what you really want to develop is called relative pitch. A person with relative pitch can do several things, all stemming from one basic ability: the ability to identify notes by comparing them by ear to a named note. This is a very important skill for all musicians.
A person with relative pitch should be able to name all the chords used in a song once they know what key it’s in. They should be able to name all the notes used in the melody based on this same knowledge. By relating back to that one piece of knowledge – a known note, or a known key – you are using the real musician’s skill of relative pitch.
So how do you develop this ability? Do an online search for “ear training software” and you’ll find dozens of programs that will help. Learning to read music is an important step. And take my advice: give perfect pitch programs a miss.