content: /*
   * Copyright (C) 2015 The Android Open Source Project
   *
   * 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.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.example.android.common.midi.synth;
  
  public abstract class SynthUnit {
  
      private static final double CONCERT_A_PITCH = 69.0;
      private static final double CONCERT_A_FREQUENCY = 440.0;
  
      /**
       * @param pitch
       *            MIDI pitch in semitones
       * @return frequency
       */
      public static double pitchToFrequency(double pitch) {
          double semitones = pitch - CONCERT_A_PITCH;
          return CONCERT_A_FREQUENCY * Math.pow(2.0, semitones / 12.0);
      }
  
      public abstract float render();
  }
  