microtonal sampler

1 files changed, 162 insertions, 0 deletions

diff --git a/client/lib/intonation.js b/client/lib/intonation.js
new file mode 100644
index 0000000..e5465af
--- /dev/null
+++ b/client/lib/intonation.js
@@ -0,0 +1,162 @@
+module.exports = (function(){
+  var Intonation = function(opt){
+    opt = this.opt = Object.assign({
+      name: "",
+      root: 440,
+      octave: 0,
+      interval: 2,
+      tet: 0,
+      intervals: null,
+    }, opt || {})
+    this.generate()
+  }
+  Intonation.prototype.generate = function(opt){
+    opt = Object.assign(this.opt, opt || {})
+    if (opt.scl) {
+      this.generate_scl()
+    }
+    else if (opt.tet) {
+      this.generate_tet()
+    }
+    else if (opt.intervals) {
+      this.generate_intervals()
+    }
+  }
+  Intonation.prototype.generate_intervals = function(){
+    var root = this.opt.root
+    var interval_list = this.opt.intervals
+    if (typeof interval_list == "string") {
+      interval_list = interval_list.split(" ")
+    }
+    this.name = this.opt.name || "interval list"
+    this.intervals = interval_list
+    this.interval = this.opt.interval = parseInterval.call(this, interval_list.pop() )
+    this.scale = interval_list.map( parseIntervalString.bind(this) ).filter(function(v){
+      return !! v
+    })
+  }
+  Intonation.prototype.generate_tet = function(){
+    var scale = this.scale = []
+    var root = this.opt.root
+    var tet = this.opt.tet
+    var interval = this.interval = this.opt.interval
+    var ratio = Math.pow( interval, 1/tet )
+    var n = root
+    scale.push(n)
+    for (var i = 0; i < tet-1; i++) {
+      n *= ratio
+      scale.push(n)
+    }
+    this.name = this.opt.name || tet + "-tone equal temperament"
+    this.intervals = null
+  }
+  Intonation.prototype.generate_scl = function(){
+    var root = this.opt.root
+    var scl = this.parse_scl( this.opt.scl )
+    this.intervals = scl.notes
+    this.interval = scl.notes.pop()
+    this.name = this.opt.name || scl.description
+    this.scale = scl.notes.map(function(v){
+      return v * root
+    })
+  }
+  Intonation.prototype.parse_scl = function(s){
+    var scl = {}
+    scl.comments = []
+    scl.notes = []
+    s.trim().split("\n").forEach(function(line){
+      // Lines beginning with an exclamation mark are regarded as comments
+      // and are to be ignored.
+      if ( line.indexOf("!") !== -1 ) {
+        scl.comments.push(line)
+      }
+      // The first (non comment) line contains a short description of the scale.
+      // If there is no description, there should be an empty line. (nb: which is falsey)
+      else if ( ! ('description' in scl) ) {
+        scl.description = line
+      }
+      // The second line contains the number of notes.
+      // The first note of 1/1 or 0.0 cents is implicit and not in the files.
+      else if ( ! scl.notes.length) {
+        scl.notes.push(1)
+      }
+      else {
+        // If the value contains a period, it is a cents value, otherwise a ratio.
+        var note = line.replace(/^[^-\.0-9]+/,"").replace(/[^-\/\.0-9]+$/,"")
+        if ( note.indexOf(".") !== -1 ) {
+          note = Math.pow( 2, (parseFloat(note) / 1200) )
+        }
+        else {
+          note = parseInterval(note)
+        }
+        if (note) {
+          scl.notes.push(note)
+        }
+      }
+    })
+    return scl
+  }
+  Intonation.prototype.index = function(i, octave){
+    octave = octave || this.opt.octave
+    var f = this.scale[ mod(i, this.scale.length)|0 ]
+    var pow = Math.floor(norm(i, 0, this.scale.length)) + octave
+    f *= Math.pow(this.interval, pow)
+    return f
+  }
+  Intonation.prototype.range = function(min, max){
+    var a = []
+    for (var i = min; i < max; i++) {
+      a.push( this.index(i) )
+    }
+    return a
+  }
+  Intonation.prototype.set_root = function(f){
+    this.opt.root = f
+    this.generate()
+  }
+  Intonation.prototype.quantize_frequency = function(f){
+    if (f == 0) return 0
+    var scale_f = f
+    var pow = 0
+    var interval = this.interval
+    var scale = this.scale
+    while (scale_f < root) {
+      scale_f *= interval
+      pow -= 1
+    }
+    while (scale_f > root * interval) {
+      scale_f /= interval
+      pow += 1
+    }
+    for (var i = 0; i < scale.length; i++) {
+      if (scale_f > scale[i]) continue
+      scale_f = scale[i]
+      break
+    }
+    scale_f *= Math.pow(2, pow)
+    return scale_f
+  }
+  Intonation.prototype.quantize_index = function(i){
+    return mod(index-1, this.scale.length)|0
+  }
+  var parseInterval = Intonation.prototype.parse_interval = function (s) {
+    if (typeof s == "number") return s
+    if (! s.indexOf("/") == -1) return parseInt(s)
+    var pp = s.split("/")
+    var num = parseInt(pp[0])
+    var den = parseInt(pp[1])
+    if (isNaN(num)) return 1
+    if (isNaN(den) || den == 0) return num
+    if (num == den) return 1
+    return num / den
+  }
+  var parseIntervalString = Intonation.prototype.parse_interval_string = function(s){
+    if (s.indexOf("/") !== -1) return parseInterval(s) * this.opt.root // intervals
+    if (s.indexOf("f") !== -1) return parseFloat(s)    // pure frequencies
+    return parseFloat(s)
+  }
+  function norm(n,a,b){ return (n-a) / (b-a) }
+  function mod(n,m){ return n-(m * Math.floor(n/m)) }
+
+  return Intonation
+})()