Scale
A scale is a set of notes in order, one step at a time, from the tonic up to the same note an octave higher. The C major scale: C, D, E, F, G, A, B, C.
A scale starts and ends on the same note, the tonic. The C major scale has eight notes from C to C, all on white keys. A scale is played both up and down. Each note has a number, its scale degree, written in Roman numerals from I to VIII.
The sound of a scale comes from the distances between its notes. The major pattern is whole, whole, half, whole, whole, whole, half (W W H W W W H). The half steps fall between E and F and between B and C, where there is no black key. Start the same pattern on G or F and you need a black key: F♯ or B♭. The natural minor has a different pattern: whole, half, whole, whole, half, whole, whole.
The right hand plays the scale with the fingering 1 2 3 1 2 3 4 5: after E, the thumb passes under the third finger and plays F. In a scale you know well, one wrong note stands out at once.
What it sounds like
A scale sounds like a staircase: every note steps up one degree, and the last one arrives home. A major scale sounds bright, a minor scale darker.
Where it is taught: the studio’s interactive textbook, chapter 6, “The C major scale”.