Learning the sound of chord progressions is important. If your dealing with melodic music there are certain progressions and common variations that occur very frequently. Once you can hear a I-vi-IV-V it doesn't matter what key it's in, they will sound the same. You'll start to notice just how often these progressions appear in music. This is also where some knowledge of theory comes into play.
It's also a good ear training exercise to people to take a simple melody, like a child's song and figure out the chords that would go underneath it...for example "The Wheels on the Bus" or "Mary Had A Little Lamb"
It's also a good ear training exercise to people to take a simple melody, like a child's song and figure out the chords that would go underneath it...for example "The Wheels on the Bus" or "Mary Had A Little Lamb"