beats.clj

(def rock
  { :snare '(_ O)
    :kick  '(O _) })

(def dnb
  ;        '(1 _ . _ 2 _ . _ 3 _ . _ 4 _ . _)
  { :snare '(_ _ _ _ O _ _ o _ o _ _ O _ _ _)
    :kick  '(O _ _ _ _ _ _ _ _ _ O _ _ _ _ _) })

(def reggae
  ;        '(1 _ . _ 2 _ . _ 3 _ . _ 4 _ . _)
  { :hihat '(O O O _ O _ O _ _ O O _ O _ O _)
    :snare '(_ _ _ _ O _ _ o _ _ _ _ O _ _ _)
    :kick  '(_ _ _ _ O _ _ _ _ _ _ _ O _ _ _) })

(defn hit-intensity
  [hit]
  (cond
    (= hit '_) 0
    (= hit 'o) 1
    (= hit 'O) 2))

(defn parse-beat-sequence
  [beat-sequence]
  (map parse-hit beat-sequence))

(defn stretch
  [beat-sequence factor]
  (mapcat #(cons % (repeat (dec factor) '_)) beat-sequence))

(defn map-beat
  [f beat]
  (into {} (for [[k v] beat] [k (f v)])))

(defn stretch-beat
  [beat factor]
  (map-beat #(stretch % factor) beat))