In the beginning, students are tested for their ability to hear the difference between high and low pitches. Two notes are played side by side and the highest or lowest must be identified. Once this is mastered we move to 3 notes and the same test is given. From this point on, ear training moves to the intervals. Students are taught to hear and identify the distances between any two notes in the chromatic one octave scale. For instance ....the distance between C and G is a perfect 5th. A perfect 5th sounds like Twinkle Twinkle Little Star. Associating songs with each interval will aid in the development of Perfect Relative Pitch.
Chord Ear Training is also explored. Hearing the difference between major, minor, diminished and augmented chords is an important skill that every musician should have.
Chord Progression Ear Training is the skill that allows your ear to hear the chords in a song and identify them in terms of their matching roman numeral, relative to the key of the song. For instance in the Key of C major, the chords C, F and G would represent roman numerals I, IV and V. This skill is essential especially for pop musicians who wish to play in a cover band and learn songs for themselves by ear. This skill will also prove invaluable for beginning songwriters!
There are many more ear training studies. The Canadian Conservatory of Music employs these exercises as part of all instrumental classes but also offers this as a separate class.