sounds.h

#include <cmath>
#include <fstream>
#include <iostream>
using namespace std;

//Adapted from http://www.cplusplus.com/forum/beginner/166954/

namespace little_endian_io {
  template <typename Word>
  
  std::ostream& write_word( std::ostream& outs, Word value, unsigned size = sizeof( Word ) ) {
    for( ; size; --size, value >>= 8 ) // value >>= 1 means "set value to itself shifted by one bit to the right".
      outs.put( static_cast <char> ( value & 0xFF ) );
    return outs;
  }
}
using namespace little_endian_io;

void output_sounds( uint8_t* notes, int notes_n ) {
	ofstream f( "output.wav", ios::binary );

	// Write the file headers
	f << "RIFF----WAVEfmt ";     // (chunk size to be filled in later)
	write_word( f,     16, 4 );  // no extension data
	write_word( f,      1, 2 );  // PCM - integer samples
	write_word( f,      2, 2 );  // two channels (stereo file)
	write_word( f,  44100, 4 );  // samples per second (Hz)
	write_word( f, 176400, 4 );  // (Sample Rate * BitsPerSample * Channels) / 8
	write_word( f,      4, 2 );  // data block size (size of two integer samples, one for each channel, in bytes)
	write_word( f,     16, 2 );  // number of bits per sample (use a multiple of 8)

	// Write the data chunk header
	size_t data_chunk_pos = f.tellp();
	f << "data----";  // (chunk size to be filled in later)
  
	// Write the audio samples
	double two_pi = 6.283185307179586476925286766559;
	double max_amplitude = 32760;  // "volume"

	double hz        = 44100;    // samples per second
	double frequency = 110;		  // A2 (25th note)
	double seconds   = 0.5;      // time
	int N = hz * seconds;  // total number of samples

	for (int n = 0; n < N; n++) {
		double c_amplitude = max_amplitude*notes[0]/255.0;
		double amplitude = (double)n / N * c_amplitude;
		double value     = sin( (two_pi * n * frequency) / hz );
		write_word( f, (int)(                 amplitude  * value), 2 );
		write_word( f, (int)((c_amplitude - amplitude) * value), 2 ); //MAX_ O C_
	}

	for( int i = 1; i < notes_n; i++ ) {
		frequency *= pow( 2, 1.0/12 );
		double c_amplitude = max_amplitude*notes[i]/255.0;
		for (int n = 0; n < N; n++) {
			
			double amplitude = (double)n / N * c_amplitude;
			
			double value     = sin( (two_pi * n * frequency) / hz );
			write_word( f, (int)(                 amplitude  * value), 2 );
			write_word( f, (int)((c_amplitude - amplitude) * value), 2 ); //MAX_ O C_
		}
	}
	
	// (We'll need the final file size to fix the chunk sizes above)
	size_t file_length = f.tellp();

	// Fix the data chunk header to contain the data size
	f.seekp( data_chunk_pos + 4 );
	write_word( f, file_length - data_chunk_pos + 8 );

	// Fix the file header to contain the proper RIFF chunk size, which is (file size - 8) bytes
	f.seekp( 0 + 4 );
	write_word( f, file_length - 8, 4 ); 
}