From 2c22abf2ea25cdaa1b3adb07d1ca2dde488b4e0a Mon Sep 17 00:00:00 2001
From: Alex Clink <alexclink@gmail.com>
Date: Sat, 19 Feb 2022 23:01:22 -0500
Subject: [PATCH] Improve piano, add harmonica

---
 examples/piano.cr       |  2 +-
 src/audio.cr            |  2 +-
 src/audio/instrument.cr | 49 ++++++++++++++++++++++++++++++++++++-----
 src/audio/note.cr       |  5 +++--
 4 files changed, 49 insertions(+), 9 deletions(-)

diff --git a/examples/piano.cr b/examples/piano.cr
index c86434a..3f4c4db 100644
--- a/examples/piano.cr
+++ b/examples/piano.cr
@@ -18,7 +18,7 @@ module PF
     @white_keys = [] of Tuple(Vector2(Int32), Vector2(Int32), String)
     @black_keys = [] of Tuple(Vector2(Int32), Vector2(Int32), String)
 
-    @instruments : Array(Instrument) = [RetroVoice.new, PianoVoice.new, Flute.new, KickDrum.new, SnareDrum.new]
+    @instruments : Array(Instrument) = [RetroVoice.new, PianoVoice.new, Flute.new, KickDrum.new, SnareDrum.new, Harmonica.new]
 
     def initialize(*args, **kwargs)
       super
diff --git a/src/audio.cr b/src/audio.cr
index 005fc36..b23be68 100644
--- a/src/audio.cr
+++ b/src/audio.cr
@@ -6,7 +6,7 @@ module PF
     @device_id : LibSDL::AudioDeviceID
     property volume = 0.5
     # https://dsp.stackexchange.com/questions/3581/algorithms-to-mix-audio-signals-without-clipping
-    property headroom = 0.4
+    property headroom = 0.3
     delegate :freq, to: @spec
     @playing : Bool = false
     getter time : Float64 = 0.0
diff --git a/src/audio/instrument.cr b/src/audio/instrument.cr
index 37d1ddc..e8d4aa9 100644
--- a/src/audio/instrument.cr
+++ b/src/audio/instrument.cr
@@ -3,6 +3,7 @@ module PF
     property name : String = "Unnamed Instrument"
     property envelope : Envelope
     property wave : Sound::Wave
+    property volume : Float64 = 1.0
 
     getter sounds : Array(Sound) = [] of Sound
     @notes : Hash(UInt32, Sound) = {} of UInt32 => Sound
@@ -13,7 +14,7 @@ module PF
 
     def on(hertz : Float64, time : Float64)
       @note_id += 1_u32
-      sound = Sound.new(hertz, @envelope, time, @wave)
+      sound = Sound.new(hertz, @envelope, time, @volume, @wave)
       @notes[@note_id] = sound
       @sounds << sound
       @note_id
@@ -47,13 +48,32 @@ module PF
   class PianoVoice < Instrument
     def initialize
       @name = "Piano"
+
+      exp_interpolation = ->(time : Float64, duration : Float64, initial : Float64, level : Float64) do
+        # https://www.desmos.com/calculator/r2jn9wurwv
+        curve = 1000
+        (initial - level) * ((curve ** -(time / duration)) * (1 + (1 / curve)) - (1 / curve)) + level
+      end
+
       @envelope = Envelope.new(
-        attack: Envelope::Stage.new(0.001, 0.0, 1.0),
-        decay: Envelope::Stage.new(0.7, 1.0, 0.0),
+        attack: Envelope::Stage.new(0.001, 0.0, 1.0, exp_interpolation),
+        decay: Envelope::Stage.new(3.0, 1.0, 0.0, exp_interpolation),
         sustain: Envelope::Stage.new(0.0, 0.0, 0.0),
-        release: Envelope::Stage.new(0.5, 1.0, 0.0)
+        release: Envelope::Stage.new(0.3, 1.0, 0.0)
       )
-      @wave = Sound.triangle_wave(6.0, 0.0005)
+
+      @wave = ->(time : Float64, hertz : Float64) do
+        # https://www.desmos.com/calculator/mnxargxllk
+        av = 2 * Math::PI * hertz * time
+        y = (Math.sin(Math::PI * (av / Math::PI)) ** 3) + Math.sin(Math::PI * ((av / Math::PI) + (2 / 3)))
+        y = (Math.sin(av) ** 3) + Math.sin(av + 0.6666)
+        y += y / 2
+        y += y / 4
+        y += y / 8
+        y += y / 16
+        y += y / 32
+        y /= 5
+      end
     end
   end
 
@@ -106,4 +126,23 @@ module PF
       end
     end
   end
+
+  class Harmonica < Instrument
+    def initialize
+      @name = "Harmonica"
+      @envelope = Envelope.new(
+        attack: Envelope::Stage.new(0.1, 0.0, 1.0),
+        decay: Envelope::Stage.new(0.3, 1.0, 0.8),
+        sustain: Envelope::Stage.new(Float64::INFINITY, 0.8, 0.8),
+        release: Envelope::Stage.new(0.3, 1.0, 0.0)
+      )
+      @volume = 0.5
+      wave = Sound.square_wave
+      @wave = ->(time : Float64, hertz : Float64) do
+        0.5 * wave.call(time + 0.1, hertz * 2) +
+        wave.call(time, hertz) +
+        rand(-0.05..0.05)
+      end
+    end
+  end
 end
diff --git a/src/audio/note.cr b/src/audio/note.cr
index 5149703..fb6d2df 100644
--- a/src/audio/note.cr
+++ b/src/audio/note.cr
@@ -1,7 +1,8 @@
 module PF
   struct Note
-    NAMES       = %w[C C#/Db D D#/Eb E F F#/Gb G G#/Ab A A#/Bb B]
-    ACCIDENTALS = StaticArray[1u8, 3u8, 6u8, 8u8, 10u8]
+    TWELFTH_ROOT = 2 ** (1 / 12)
+    NAMES        = %w[C C#/Db D D#/Eb E F F#/Gb G G#/Ab A A#/Bb B]
+    ACCIDENTALS  = StaticArray[1u8, 3u8, 6u8, 8u8, 10u8]
 
     getter tuning : Float64 = 440.0
     getter number : Float64