Use middle C = C4

This retains compatibility with danigb's soundfont player

README.md

@@ -9,15 +9,17 @@ This is an experimental complete re-write of the soundfont library.  Although st
 
 A SoundFont can be loaded from Benjamin Gleitzman's package of [pre-rendered sound fonts](https://github.com/gleitz/midi-js-soundfonts) or from a resource on the local server. It is then decoded into a dictionary of Audio Buffers (one for each note).  A succession of notes can then be played through these buffers.
 
-This is intended to be functionally equivalent to purescript-polymorphic soundfonts.  The major difference from a user perspective is that the soundfonts are no longer implicit and have to be stored by the user and passed to the __playNote__ functions.  The rarely used function to get the current time from the Audio Context has been dropped. 
+The conversion of a Gleitzman note name (e.g. Ab4) to a MIDI pitch uses middle C = C4.
+
+This is intended to be functionally equivalent to purescript-polymorphic soundfonts.  The major difference from a user perspective is that the soundfonts are no longer implicit and have to be stored by the user and passed to the __playNote__ functions.  The rarely used function to get the current time from the Audio Context has been dropped.
 
 ## Build
 
     bower install   
     pulp build
-   
+
 ## Example
 
     ./build-example.sh
 
-host on your web server and then navigate to dist/index.html
+host on your web server and then navigate to dist/index.html

src/Audio/SoundFont/Gleitz.purs

@@ -8,7 +8,7 @@ module Audio.SoundFont.Gleitz (
   ) where
 
 
-import Prelude (class Show, (<>), ($), (+), (*), map, negate, show)
+import Prelude (class Show, (<>), ($), (+), (-), (*), map, negate, show)
 import Data.String.Regex as Regex
 import Data.String.Regex.Flags (noFlags)
 import Data.String (toUpper)
@@ -72,22 +72,31 @@ midiPitch1 s =
       let
         mpitch :: Maybe Int
         mpitch = case index matches 1 of       -- first match group
-          Just (Just p) -> lookup p semitones
+          Just (Just p) -> lookup p semitones  -- A-G
           _ -> Nothing
         acc :: Int
         acc = case index matches 2 of          -- second match group
-          Just (Just "b") -> (-1)
+          Just (Just "b") -> (-1)              -- # or b
+          Just (Just "#") -> 1              -- # or b
           _ -> 0
         moctave :: Maybe Int
         moctave =                              -- third match group
-          case index matches 3 of
+          case index matches 3 of              -- octave number
             Just (Just octave) -> fromString octave
             _ -> Nothing
       in
         case (Tuple mpitch moctave) of
-          (Tuple (Just p) (Just oct)) -> Just ((12 * oct) + p + acc)
+          (Tuple (Just p) (Just oct)) -> Just $ toMidiPitch oct p acc
           _ -> Nothing
 
+-- | build a MIDI pitch (middle C = C4)
+-- | building from the octave number, pitch (relative to C)
+-- | and any accidental offset (i.e. flat lowers pitch by 1, sharp raised it)
+-- | The MIDI standard does not standardise on a particular middle C
+toMidiPitch :: Int -> Int -> Int -> Int
+toMidiPitch octave pitch accidental =
+  (12 * octave) + pitch + accidental - 12
+
 lookupPitch :: Pitch -> Maybe Int
 lookupPitch p =
   lookup (toUpper p) semitones
@@ -101,7 +110,7 @@ gleitzNoteName s =
   let
     makeRegex :: Partial => Regex.Regex
     makeRegex =
-      case Regex.regex "([A-Ga-g])(b?)([0-8])" noFlags of
+      case Regex.regex "([A-Ga-g])([b#]?)([0-8])" noFlags of
         Right r ->
           r
     regex = unsafePartial makeRegex

test/Main.purs

@@ -15,12 +15,16 @@ import Audio.SoundFont.Gleitz (midiPitch)
 gleitzSuite :: forall t. Free (TestF t) Unit
 gleitzSuite =
   suite "gleitz" do
-    test "midi pitch Bb0" do
-      Assert.equal 10 (midiPitch "Bb0")
-    test "midi pitch A3" do
-      Assert.equal 45 (midiPitch "A3")
+    test "midi pitch C4" do
+      Assert.equal 36 (midiPitch "C4")
+    test "midi pitch Bb1" do
+      Assert.equal 10 (midiPitch "Bb1")
+    test "midi pitch A#1" do
+      Assert.equal 10 (midiPitch "A#1")
+    test "midi pitch A4" do
+      Assert.equal 45 (midiPitch "A4")
     test "midi pitch C8" do
-      Assert.equal 96 (midiPitch "C8")
+      Assert.equal 84 (midiPitch "C8")
 
 main :: forall t.
         Eff