What do the indexes of sound volume of the SplitAudioAnalysis Node represent?



I am working on a basic audio visualizer and I would like to know what each index represents. As currently, only index 1 and 2 seem to react to the song.



these are the frequency bands of the FFT (Dshow9 4Channels):
0 = bass
1 = low mids
2 = high mids
3 = highs


Noted, thank you!