core.clj

(ns amen.core
  (:require [overtone.live :refer :all]))

(def snare     (freesound 26903))
(def crash     (freesound 26884))
(def ride      (freesound 26889))
(def kick      (freesound 26888))

(def amen-tabs
  [{:sound crash, :tab "----------------|----------------|----------------|----------x-----"}
   {:sound ride,  :tab "x-x-x-x-x-x-x-x-|x-x-x-x-x-x-x-x-|x-x-x-x-x-x-x-x-|x-x-x-x-x---x-x-"}
   {:sound snare, :tab "----x--x-x--x--x|----x--x-x--x--x|----x--x-x----x-|-x--x--x-x----x-"}
   {:sound kick,  :tab "x-x-------xx----|x-x-------xx----|x-x-------x-----|--xx------x-----"}])

(def amen-nome (metronome 136))
(def one-twenty (metronome 120))

(defn tab-to-offsets
  "Converts <tab> to a sequence of numerical beat offsets. <tab> should be a
  string of semiquaver tablature, with '-' denoting a rest, 'x' denoting a hit,
  and '|' delimiting bars."
  ([tab] (tab-to-offsets 0 tab))
  ([pos tab]
   (when (seq tab)
     (case (first tab)
       \x (cons pos (tab-to-offsets (+ pos 1/4) (rest tab)))
       \- (recur (+ pos 1/4) (rest tab))
       (recur pos (rest tab))))))

(defn play-tab
  "Plays a given <tab> on a beat specified by <nome>, starting at the specified
  <beat>."
  [nome beat tab]
  (let [offsets (tab-to-offsets (:tab tab))]
    (map #(at (nome (+ beat %)) ((:sound tab))) offsets)))

(defn play-tabs [nome tabs]
  (let [beat (inc (nome))]
    (map (partial play-tab nome beat) tabs)))

(play-tabs amen-nome amen-tabs)