XAudio2 SetFrequencyRatio() doesn't seem to work

Question

SetFrequencyRatio() does not seem to work for me. Below is the source code I'm using. It reads the frequency with GetFrequencyRatio before and after calling SetFrequencyRatio(1.3). But it prints out 1.0 even after the call to SetFrequencyRatio(1.3) and I don't know why. What am I doing wrong?

#include <windows.h>
#include <stdio.h>
#include <XAudio2.h>

int WINAPI WinMain(HINSTANCE hinstance, HINSTANCE hprevinstance, LPSTR lpcmdline, int ncmdshow) {
    WAVEFORMATEX format;
    format.wFormatTag = 1;
    format.nChannels = 1;
    format.nSamplesPerSec = 44100;
    format.nAvgBytesPerSec = 44100;
    format.nBlockAlign = 1;
    format.wBitsPerSample = 8;
    format.cbSize = 0;

    CoInitializeEx(NULL, COINIT_MULTITHREADED);

    IXAudio2* pXAudio2 = NULL;
    IXAudio2SourceVoice* source = NULL;
    IXAudio2MasteringVoice* master = NULL;

    HRESULT hr;
    if ( FAILED(hr = XAudio2Create( &pXAudio2, 0, XAUDIO2_DEFAULT_PROCESSOR ) ) ) {
        MessageBox(0, L"hi", L"hi", 0);
        return hr;
    }

    if ( FAILED(hr = pXAudio2->CreateMasteringVoice(&master ) ) ) {
        MessageBox(0, L"hi", L"hi", 0);
        return hr;
    }

    if ( FAILED(hr = pXAudio2->CreateSourceVoice(&source, &format, 0, XAUDIO2_MAX_FREQ_RATIO ) ) ) {
        MessageBox(0, L"hi", L"hi", 0);
        return hr;
    }

    float freq = 0.0;
    source->GetFrequencyRatio(&freq);

    char str[30];
    sprintf(str, "%f", freq);
    MessageBoxA(0, str, str, 0);

    if ( FAILED(hr = source->SetFrequencyRatio(1.3) ) ) {
        MessageBox(0, L"hi", L"hi", 0);
        return hr;
    }
    pXAudio2->CommitChanges(0);

    source->GetFrequencyRatio(&freq);
    sprintf(str, "%f", freq);
    MessageBoxA(0, str, str, 0);

    return 0;
}