fft – How to increase the low frequency resolution of spectrum of music signal

I know normal FFT with a fixed window size will introduce leakage and rectangular window function will give me the best main lobe width.

For example, with 44100Hz sample rate, 2048 window size, a 64Hz sine wave will have about 20~30Hz resolution in a VST plugin called Voxengo SPAN.

enter image description here

However, in Image-Line Wave Candy and Edison, with the same configuration (44100Hz sample rate, 2048 window size), it can have nearly 1Hz resolution. (I’m not sure Image-Line plugins use FFT but I can confirm Voxengo’s uses FFT because they stated in their documents)
enter image description here

My question is how to achieve the spectrum resolution like Image-Line’s plugins without increasing window size (limited by time resolution) or sample rate? Whether with DFT-based algorithm or other algorithms.
The input signal is audio signal (20Hz-20kHz). It is not always sine wave. It could be polyphonic and complicated waveforms.


From @Dan Boschen’s suggestion I tried to place two sine wave as close as possible before aliasing. It seems it is not really 1Hz resolution. (about 15Hz minimal I can get before this happens visually)
enter image description here

I also tried a linear chirp signal from 440Hz to 44hz in 8192 samples. It is like this.
enter image description here

Although it is not 1Hz resolution, their result is still what I want to achieve. So I will try zero padding later.

Read more here: Source link