Scales, Modes and Key Signatures

This module builds toward the working musician’s core reflex: given any root note, spell every scale you need without a lookup table. In a live-coding set or a studio session, scale choice is mood choice — a Phrygian bassline reads as psy-trance menace, a Lydian pad as euphoria, a pentatonic lead as instantly singable — and you rarely have time to google “F# Dorian” mid-pattern. The capstone reference sheet is the artifact every producer secretly keeps taped above the keyboard; here you earn it by deriving every row yourself.

The arc starts fully supported: apply the tone-semitone pattern of the major scale to your chosen root, checking yourself against the chromatic semitone grid. From there each step is a controlled mutation of what you just built — flatten degrees to get natural minor, raise the 7th for the harmonic form (and hear why cadences demand it), smooth the ascent for melodic minor. The relative-key relationship and the cycle of fifths then let you place your key among all twelve, deriving its signature instead of memorizing it. Rotating your major scale through all seven starting degrees yields the modes; the Mixolydian deep-dive models how a single characteristic degree gives a mode its identity — exactly the skill your unsupported 8-bar melody must demonstrate. Pentatonic and exotic-scale atoms round out the palette for the sheet’s final rows.

Every required atom gates a specific row of the sheet or the melody itself; the module fails without any one of them. The supporting atoms — chromatic semitones, interval naming, the scale-degrees-versus-intervals distinction, and pentatonic rotations — sharpen your fluency and vocabulary but the capstone stands without them. Drill the major and minor patterns and the cycle of fifths until they are automatic: they recur in every later harmony module.

Walkthrough

The reference sheet is the theory; the live-coder’s reflex is hearing a scale choice as a mood choice. At strudel.cc (Ctrl-Enter play, Ctrl-. stop) we play scale degrees through n(...).scale(...), so 0 is always the root, 2 the third, and so on — change the scale name and the same degrees relocate to a new mood. Each step is a complete, playable program.

1 — degrees in a key. n("0 1 2 3 4 5 6 7") are scale degrees; .scale("C:major") maps them onto C major. Everything sounds “right” because you can only land on in-key notes — the whole point of thinking in degrees ([[major-scale-tone-semitone-pattern]]).

n("0 2 4 5 7 9 11 12").scale("C:major").sound("triangle")

2 — same shape, new key. Change only the root and the melody transposes wholesale — the degrees don’t move, the key does ([[relative-major-minor-keys]]).

n("0 2 4 5 7 9 11 12").scale("A:major").sound("triangle")

3 — minor: flatten the mood. C:minor lowers the 3rd, 6th and 7th — same degree numbers, darker colour. This is the major/minor switch every producer reaches for first ([[natural-minor-scale-pattern]]).

n("0 2 4 5 7 9 11 12").scale("C:minor").sound("triangle")

4 — the modes are moods. Rotate the scale and you get the seven modes, each with a characteristic degree: mixolydian is major with a flat 7 (bluesy, hip-hop), dorian minor with a raised 6 (jazzy, hopeful) ([[seven-diatonic-modes]], [[mixolydian-mode]]). Same degrees, different world:

$: n("0 2 4 5 7 9 11 12").scale("G:mixolydian").sound("triangle")

5 — pentatonic and exotic. Drop to five notes for instant singability (major pentatonic — nothing clashes), or reach for a flavour: phrygian reads as psy-trance menace from its flat 2nd ([[pentatonic-scale]], [[exotic-scales-world-music]]).

$: n("0 1 2 3 4").scale("C:major pentatonic").sound("triangle")
$: n("0 1 2 3 4").scale("E:phrygian").sound("sawtooth").lpf(700)

6 — an 8-bar melody that lives in one mode (the capstone). Pick a mode and write a melody that shows its character. This one sits in A Dorian — the raised 6th (degree 5 here) gives it that hopeful minor lift — with a bassline on the root and fifth to anchor the key:

setcpm(96/4)
$: n("0 2 4 <5 4> 2 4 <2 0> ~").scale("A:dorian").sound("triangle").gain(0.9)
$: n("<0 4>").scale("A:dorian").sound("sawtooth").lpf(600)
$: sound("bd ~ ~ ~ bd ~ ~ ~").bank("RolandTR909")

What good sounds like. A melody that could only be that mode — you should be able to hum it and feel the flat-7 or raised-6 that makes it distinctive, not just “some notes in a key.” If it sounds generic, lean harder on the characteristic degree (for Dorian, hit that raised 6th; for Phrygian, the flat 2nd). Staying in one scale means nothing clashes — the freedom is in the rhythm and contour, not in dodging wrong notes. (Skill map: live-coder Domain B3 — scales, modes, staying in key.)

Now make it yours. Swap A:dorian for A:phrygian and hear the mood darken with no other change. Move the bass to <0 3 4>. Try C:lydian (raised 4th) for euphoria. Rewrite the melody’s rhythm with ~ rests and [..] subdivisions while keeping the same degrees.