Scales and Scale Degrees

Scales can be quickly generated using the scale function, which takes a root note and the type of scale as arguments.

(scale :C3 :major)
; => (48 50 52 53 55 57 59 60)

The available scales are quite large, which includes the common major/minor, modes (dorian, mixolydian, etc.), and more exotic scales. You can see the full list by running the following command in your REPL:

(source SCALE)

Overtone is also capable further abstraction of pitches through scale degrees, which is a way of referring to pitches within a scale. Scale degrees are commonly notated using roman numerals (I, IV, vii, etc.), so in Clojure scale degrees are referenced with keywords as shown below:

(def scale-degrees [:i :ii :iii :iv :v :vi :vii])

Notice that each of the scale degrees is lowercase; Overtone does not change the quality of the scale degree based on capitalization. Capitalized degrees will throw an IllegalArgumentException.

You can resolve scale degrees into absolute pitches using degrees->pitches:

(degrees->pitches scale-degrees :dorian :E3)
; => (52 54 55 57 59 61 62)

Scale degrees can be augmented by either + or - to denote the octave above or below the root of the scale, and can be sharped or flatted using # or b. For example in a major scale starting from C3 (MIDI pitch number 48), the scale degree :ib+ would be resolved to a Cb4 (MIDI pitch number 59).

Another useful feature of scale degrees in Overtone is the :_ keyword, which you can use to denote rests. Below is an example that uses both note ornament and the :_ nil value:

(def scale-degrees [:vi :vii :i+ :_ :vii :_ :i+ :vii :vi :_ :vii :_])
(def pitches (degrees->pitches scale-degrees :dorian :C4))

(defn play [time notes sep]
  (let [note (first notes)]
    (when note
      (at time (saw (midi->hz note))))
    (let [next-time (+ time sep)]
      (apply-at next-time play [next-time (rest notes) sep]))))