Well in many kicks you find there is a part where the pitch is a steady sine.
This part at least is tuneable. I read today that in those lower regions of the spectrum you'd want 60ms at least of steady pitch to be able to identify the pitch. In pretty much all kicks i looked at recently this is holds true. I enjoy putting my kickdrums together in an audio-editor. Audacity is free and absolutely capable. You can clean up sampled kicks to the tee, build your own, make hybrids etc.