An interval defines the distance between two pitches. The sound quality of an interval remains the same over a wide range of pitches from high to low. For example, you can move a song into a higher or lower key by starting on another pitch. The shape and character of the melody stays the same because the intervals it uses remain the same. The study of intervals, scales, and chords leads to a sense of relative pitch even for someone without absolute pitch .
Ear training starts with practice and memorization of intervals.
The difficulty comes when we try to explain how to read and write them. This requires knowledge of note names, staff notation, half steps, scales, and the naming of intervals by quality and number. However, beginners can skip ahead and get right to work with ear training by using solfeggio. We can recognize the sound of this interval before knowing that it is a minor third or that it contains three half steps or that it can be written e-g on the staff. It is possible to start beginners with ear training at the very beginning of music study using solfeggio.