Tetrachords
All major scales can be split in half, into two major tetrachords (a 4-note segment with the pattern 2-2-1, or whole-step, whole-step, half-step). It’s much easier to remember 4-note patterns than 7 or 8-note patterns, so breaking it down into two parts can be very helpful.
The lower tetrachord of an E flat major scale is made up of the notes Eb, F, G, and Ab.
The upper tetrachord is made up of the notes Bb, C, D, and Eb.
These two 4-note segments are joined by a whole-step in the middle.
It’s helpful to see this on a piano diagram:
