Basic Monophonic synthesiser error Xcode

int main ()
{
    int note, velocity;
    int playingNote = -1;
    float frequency;
    printf("play the Axiom\n");

    while(true)
    {
        note = aserveGetNote();
        velocity = aserveGetVelocity();

        if(velocity > 0)
        {
            frequency = 440 * pow(2, (note-69) / 12.0);
            aserveOscillator(0, frequency, 1.0, 0);
            playingNote = note;
        }
        else if(note == playingNote)
        {
            aserveOscillator(0, 0, 0, 0);
        }

    }
    return 0;
}

if(velocity > 0)
{
    frequency = 440 * pow(2,(note-69)/12.0);

    printf("note = %d\n", note);
    printf("frequency = %f\n", frequency);

    aserveOscillator(0, frequency, 1.0, 0);

}

else if(note == playingNote)
{
    aserveOscillator(0, 0, 0, 0);
}

This is supposed to run a simple monophonic synth. I get error messages on if(velocity >0) saying "expected unqualified - id" and on else if(note == playingNote) I get these error messages a lot in coding, can anyone help me out?