I did my initial tests using the spectrum sample from bass and white noise. I expected to see the band in the graph move as slide the frequency. But probably I didn't see it move because the graph scale was also changing.
Yes, just like the EQ centre frequency is affected by the sample rate, so is the FFT. You could use the LIVESPEC example to capture and display the sound, as that will have a fixed sample rate, so its display frequency range won't change.
This is good, however I also need to somehow simulate somehow the other behavior in which the equalizer is not affected by sample rate.
input --> equalizer filter(affected by sample rate, this is a inverse RIAA equalizer filter in order to simulate original vinyl sound) --> sample rate change filter --> equalizer filter(not affected by sample rate, this is a output RIAA equalizer filter) --> output
I've noticed in the Bass FX "tempo" sample that when BASS_ATTRIB_TEMPO_FREQ was changed, a manual correction of the bands center was applied. This is not the case for BASS_ATTRIB_FREQ?
The difference when changing the rate via BASS_FX's tempo processing (BASS_ATTRIB_TEMPO_FREQ) is that the output sample rate doesn't change (BASS_FX resamples the source to sound like the requested rate), so EQ/FFT frequencies are unchanged.