Just simply zero every even or odd sample, with some simple ramp when it turns on or off to prevent 'clicks'.
Superpowered doesn't really offer a function for such tiny task. You can do it with the SuperpoweredStereoMixer, but it may be too complex for this simple job.
Here is code snippet
bool Tempo::process(short int *output, unsigned int numberOfSamples) {
bool silence = !playerA->process(stereoBuffer, false, numberOfSamples, volA);
echo->process(stereoBuffer, stereoBuffer, numberOfSamples);
reverb->process(stereoBuffer, stereoBuffer, numberOfSamples);
float *mixerInputs[4] = {stereoBuffer, NULL, NULL, NULL};
float *mixerOutputs[2] = {stereoBuffer, NULL};
float mixerInputLevels[8] = {1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f};
float mixerOutputLevels[2] = {left, right};
mixer->process(mixerInputs, mixerOutputs, mixerInputLevels, mixerOutputLevels, NULL, NULL,
numberOfSamples);
if (!silence) {
SuperpoweredFloatToShortInt(mixerOutputs[0], output, numberOfSamples);
}
return !silence;
}