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;; tenor/constructs.clj
;; Primitive components of music theory.
(ns tenor.constructs
(:use []))
;; --- Notes --- ;;
(defn make-note [notation]
"Take pitch letter + octave notation
and generate an overtone note keyword."
(let [notation-re #"^([A-G])([#b]?)([1-9])$"
components (re-matches notation-re notation)]
(if components
(keyword (reduce str (rest components)))
(throw (Exception. "Invalid notation")))))
;; --- Time Signature --- ;;
(defn generate-meter [beat-count & [sig]]
"Decompose a measure into a random meter of beats,
within the time signature's note count."
(> beat-count 3)
(let [beat (rand-nth [2 3 4])
sig (conj (or sig '()) beat)]
(generate-meter (- beat-count beat) sig))
(and (<= beat-count 3) (> beat-count 0))
(let [sig (conj (or sig '()) beat-count)]
(generate-meter 0 sig))
:else sig))
;; --- Beats --- ;;;
(defn segment-beat [beat-count note-value
& {:keys [sparseness]
:or {sparseness 1}}]
"Break a beat down into sixteenth-note positions and
assign notes and rests to each position by iteration."
(let [sixteenth-count (* (/ 16 note-value) beat-count)
notes (range 1 (inc sixteenth-count))
distribution (cons true (repeat sparseness false))]
(fn [x] (or (= 1 x) (rand-nth distribution)))
;; --- Scales --- ;;;
(defn generate-random-scale []
"Generate a random scale (Example - :E3 :Dorian)."
(let [scale-type (rand-nth (keys SCALE))
ninth-octave-count 131
note-name (find-note-name (rand-int ninth-octave-count))]
(scale note-name scale-type)))
;; --- Measures --- ;;;
(defn segment-measure [measure
& {:keys [running-count result note-value sparseness]
:or {running-count 0 result '()
note-value 16 sparseness 1}}]
"Segment a measure into beats and further segment the beats,
essentially breaking the measure down into sixteenth-notes."
(if (empty? measure)
(let [result (concat result (map #(+ running-count %)
(segment-beat (first measure)
:sparseness sparseness)))
running-count (+ running-count (* (/ 16 note-value) (first measure)))]
(segment-measure (rest measure)
:running-count running-count
:result result
:note-value note-value
:sparseness sparseness))))
(defn string-measures [measures beat-count
& {:keys [running-string running-count]
:or {running-string '() running-count 0}}]
"String multiple measures together into a single piece."
(if (empty? measures)
(let [running-string (concat
(map #(+ running-count %) (first measures)))
running-count (+ running-count beat-count)]
(string-measures (rest measures)
:running-string running-string
:running-count running-count))))
;; --- Intervals --- ;;
(defn construct-intervals [construct-melody scale note-count
& {:keys [running-interval degree]
:or {running-interval '()
degree 1}}]
"Build an interval-representation of the melody
by traversing through the scale in steps/leaps/octave jumps."
(if (<= note-count 0)
(let [degree (construct-melody scale degree)
running-interval (concat running-interval (list degree))
note-count (dec note-count)]
(construct-intervals construct-melody
:degree degree
:running-interval running-interval))))
(defn generate-intervals [construct-melody scale note-count]
"Start from the first note, construct intervals,
end at the first or last note."
(let [mid-intervals (construct-intervals construct-melody scale (- note-count 2))
scale-count (count scale)]
(concat '(1)
(list (rand-nth `(1 ~scale-count))))))
(defn intervals->notes [intervals scale]
"Convert intervals to notes in a scale."
(map #(nth scale (dec %)) intervals))
;; --- Musical piece --- ;;
(defn map-entity [entity intervals]
"Create a list of hash-maps of positions as keys
and musical notes as values."
(map #(hash-map :pos %1, :note %2) entity intervals))
(defn generate-rhythm [measure-count beat-count
& {:keys [note-value sparseness]
:or {note-value 16 sparseness 1}}]
"Generate a rhythm with measure-count measures,
each of time signature with beat-count and note-value."
(let [time-sig (generate-meter beat-count)
segmented (segment-measure time-sig note-value sparseness)
rhythm (repeat measure-count segmented)]
(string-measures rhythm beat-count)))
(defn generate-entity-map [construct-melody measure-count beat-count
& {:keys [note-value sparseness scale]
:or {note-value 16
sparseness 1
scale (generate-random-scale)}}]
"Take a function to construct a melody, measure count, note count and note value,
and generate a measure map of the melody and rhythm using map-entity."
(let [rhythm (generate-rhythm measure-count beat-count note-value sparseness)
scale-intervals (intervals->notes
(generate-intervals construct-melody scale (count rhythm)) scale)]
(map-entity rhythm scale-intervals)))
;; --- Chords --- ;;
(defn chordify [entity-map construct-harmony]
"Map an external procedure that constructs chords from notes,
to the entire map of notes and positions."
(filter (fn [x] (not (nil? x)))
(map #(if (weighted-coin 0.33)
(construct-harmony (:pos %) (:note %))) entity-map)))
;; --- Playback --- ;;
(defmacro play-note [position base-time player entity]
"Take time, instrument and note entity as arguments,
and return overtone code that plays the note."
`(list 'at
`(+ ~(symbol "time") ~(* ~position ~base-time))
(list ~player ~entity)))
(defmacro construct-piece [entity-maps base-time player]
"Take an entity map and run play-note on each
note, creating a list of overtone playback code components."
`(map #(play-note (:pos %) ~base-time ~player (:note %)) ~entity-maps))
(defn play-piece [entity-maps base-time player
& {:keys [pivot-time] :or {pivot-time (now)}}]
"Play the constructed piece with current time as start time."
(let [pivot-time (symbol "time")]
`(let [~pivot-time (now)]
~@(construct-piece entity-maps base-time player))))
;; --- Multiple voices --- ;;
(defn generate-parallel-voices [& body]
"Run multiple pieces concurrently using pmap."
(pmap #(eval %) `(list ~@body)))