I'm looking for anyone who has been successful at manipulating the audio playback rate of samples when using the internal 12 bit DAC.

I have played with using someone else's code when using the Audio Shield
"setI2SmasterClock(uint32_t freq, uint32_t mult)" and this does allow changing the playback rate of samples but only when using the Audio Shield.

I really only need a mono audio output and 12bits is good enough for the project I'm working on. Sure would be nice if there was a way to get similar results using the processor's 12bit DAC instead.
If I apply the above method when using the internal DAC, and slow down the "setI2SmasterClock" rate, I can see where a block is sent, then a void in the waveform, then another block sent. Is there anyway to control transmission of individual samples to the DAC instead of blocks?

Anyone have some advice on how to make that happen?

I can't seem to get my head around what's going on with AudioStream and how it's updating the DAC.