Possibly nothing. Waveforms do not have to be symmetrical and bass notes often are not.
If you use the DC offset correction option in the Normalize effect (with “Normalize To” de-selected) and the waveform is unchanged, then there is no DC offset (just an asymmetrical waveform).
You could create a label track with labels positioned at each beat, then align your notes to the labels.
There is a plug-in for creating labels on each beat hear: Beat Per Minute labels - #13 by steve