Resolution in the frequency domain can be significantly improved over the natural resolution of the DFT (19 Hz in your case). If the fundamental frequency exact

Resolution in the frequency domain can be significantly improved over the natural resolution of the DFT (19 Hz in your case). If the fundamental frequency exactly matches one of the DFT bin frequencies, it would mean the frame size is an exact multiple of the period, so the DFT of successive frames would look the same, and there would be no phase shift at the fundamental component. (Or if overlapping frames were analyzed, there would be an expected phase shift in proportion to amount of overlap.) In the more likely case that the fundamental doesn't match a bin frequency, there's a phase shift between successive frames that's proportional to difference between the fundamental and the associated bin frequency. This can be extracted to get a more accurate estimate of the actual fundamental. I wrote a STFT-based chromatic tuner as a hobby project using this technique and it would easily resolve better than .1 Hz changes using 10(ish) ms frame sizes.