halve the speed of a wav in csharp

main.cs
using NAudio.Wave;

// Load the WAV file
var reader = new WaveFileReader("input.wav");

// Create a new WAV file to write to
var writer = new WaveFileWriter("output.wav", reader.WaveFormat);

// Change the speed of the input WAV file
var soundTouch = new SoundTouch(reader.WaveFormat.SampleRate, 
                                 reader.WaveFormat.Channels);
soundTouch.Tempo = 0.5f;

// Loop through each block of samples and write them to the output WAV file
var buffer = new float[reader.WaveFormat.SampleRate * reader.WaveFormat.Channels];
int bytesRead;
do
{
    bytesRead = reader.ReadSamples(buffer, 0, buffer.Length);
    soundTouch.PutSamples(buffer, bytesRead / reader.WaveFormat.Channels);
    int samplesAvailable;
    do
    {
        samplesAvailable = soundTouch.ReceiveSamples(buffer, 0, buffer.Length);
        writer.WriteSamples(buffer, 0, samplesAvailable * reader.WaveFormat.Channels);
    } while (samplesAvailable > 0);
} while (bytesRead > 0);

// Clean up
reader.Close();
writer.Close();
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