Merge pull request #41 from philburk/instruments

Instruments

1 files changed, 29 insertions, 5 deletions

diff --git a/src/com/softsynth/math/AudioMath.java b/src/com/softsynth/math/AudioMath.java
index 64f064f..6d5ab07 100644
--- a/src/com/softsynth/math/AudioMath.java
+++ b/src/com/softsynth/math/AudioMath.java
@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *     http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -18,7 +18,7 @@ package com.softsynth.math;
 
 /**
  * Miscellaneous math functions useful in Audio
- * 
+ *
  * @author (C) 1998 Phil Burk
  */
 public class AudioMath {
@@ -26,6 +26,7 @@ public class AudioMath {
     private final static double a2dScalar = 20.0 / Math.log(10.0);
     public static final int CONCERT_A_PITCH = 69;
     public static final double CONCERT_A_FREQUENCY = 440.0;
+    private static double mConcertAFrequency = CONCERT_A_FREQUENCY;
 
     /**
      * Convert amplitude to decibels. 1.0 is zero dB. 0.5 is -6.02 dB.
@@ -47,7 +48,7 @@ public class AudioMath {
      * Calculate MIDI pitch based on frequency in Hertz. Middle C is 60.0.
      */
     public static double frequencyToPitch(double frequency) {
-        return CONCERT_A_PITCH + 12 * Math.log(frequency / CONCERT_A_FREQUENCY) / Math.log(2.0);
+        return CONCERT_A_PITCH + 12 * Math.log(frequency / mConcertAFrequency) / Math.log(2.0);
     }
 
     /**
@@ -55,6 +56,29 @@ public class AudioMath {
      * pitches so 60.5 would give you a pitch half way between C and C#.
      */
     public static double pitchToFrequency(double pitch) {
-        return CONCERT_A_FREQUENCY * Math.pow(2.0, ((pitch - CONCERT_A_PITCH) * (1.0 / 12.0)));
+        return mConcertAFrequency * Math.pow(2.0, ((pitch - CONCERT_A_PITCH) * (1.0 / 12.0)));
+    }
+
+    /**
+     * This can be used to globally adjust the tuning in JSyn from Concert A at 440.0 Hz to
+     * a slightly different frequency. Some orchestras use a higher frequency, eg. 441.0.
+     * This value will be used by pitchToFrequency() and frequencyToPitch().
+     *
+     * @param concertAFrequency
+     */
+    public static void setConcertAFrequency(double concertAFrequency) {
+        mConcertAFrequency = concertAFrequency;
+    }
+
+    public static double getConcertAFrequency() {
+        return mConcertAFrequency;
+    }
+
+    /** Convert a delta value in semitones to a frequency multiplier.
+     * @param semitones
+     * @return scaler For example 2.0 for an input of 12.0 semitones.
+     */
+    public static double semitonesToFrequencyScaler(double semitones) {
+        return Math.pow(2.0, semitones / 12.0);
     }
 }