Possible Buffer Underrun Issues Causing Noisy Playback

I am trying to make a sequence synthesizer and feel like I am so close to the finish line but I am having a weird issue. When there are no oscillators feeding the buffer its silent, like it should be. But once even one oscillator starts feeding the buffer there is a lot of noise that is also played out. I am testing this in exclusive event driven rendering so I believe I am filling up the buffer properly but perhaps it takes too long to fill the buffer and that is creating underrun?

hr = _RenderClient->GetBuffer(_BufferSizePerPeriod, &data);
		if (SUCCEEDED(hr))
		{

			soundOutputPtr->audioOut((float *) data, _BufferSizePerPeriod, channels, 0, 0);

			hr = _RenderClient->ReleaseBuffer(_BufferSizePerPeriod, 0);
		}

Here is the code that passes the buffer to get filled

for (int i = 0; i < bufferSize/nChannels; i++){

		double sample = 0;
		int it = waves.size();
		for (int j = 0; j < it; j++){
			float val = waves[j].getSample();
			soundBuffers[j][i] = val;
			sample += val;
		}

		output[i*nChannels    ] = sample;
		output[i*nChannels + 1] = sample;

		soundBuffer[i] = sample;
	}

and this fills the buffer.

waves is a vector filled with oscillators of various types, sine, sawtooth etc...

float oscillator::getSample(){
    phase += phaseAdder;
    while (phase > TWO_PI) phase -= TWO_PI;
    if (type == sineWave){
        return sin(phase) * volume;
    } else if (type == squareWave){
        return (sin(phase) > 0 ? 1 : -1) * volume;
    } else if (type == triangleWave){
        float pct = phase / TWO_PI;
        return ( pct < 0.5 ? ofMap(pct, 0, 0.5, -1, 1) : ofMap(pct, 0.5, 1.0, 1, -1)) * volume;
    } else if (type == sawWave){
        float pct = phase / TWO_PI;
        return ofMap(pct, 0, 1, -1, 1) * volume;
    } else if (type == sawWaveReverse){
        float pct = phase / TWO_PI;
        return ofMap(pct, 0, 1, 1, -1) * volume;
    }
}

I can't really find anything as to why there would be a lot of white noise that is being played out so underrun is my only guess. has anyone else experienced this?