Leaps and thirds
Write down melodies whose notes skip a degree or more.
Skipping a degree
When a melody skips one note of the scale, the result is a third. To the ear it is a small but noticeable leap, wider than a step to the neighbouring note.
Check yourself: sing the skipped note in your head. If exactly one note "fits" between the two, it is a third.
A melody with thirds in C major
Practice: Thirds in C major
Practice: Thirds in F major
Leaps along the triad
In simple melodies, wider leaps most often follow the notes of the tonic triad: degrees I, III and V (C, E and G in C major). The ear recognises these notes easily: they are stable, the "pillars" of the key.
The melody opens with the C major tonic triad and steps down to the tonic
When you hear a wide leap, first check whether it lands on a note of the triad. Most of the time, it does.