There is something about a good bassline. Now I don't want to go into all the technical mumbo-jumbo of how it keeps the entire band 'tight' and the melody in rhythm and all that. If interested, just look it up on google. No. What I mean is, a good bassline will keep you tapped into the song right from the beginning and until the end. Since the bass sound is deeper, it resonates more inside. I really don't know the technical details as to how and what frequencies produce vibrations etc. I'm just trying to put down what I feel when I hear a brilliant bassline. I'm listening to Strip the Soul (In Absentia) by Porcupine Tree and it has a beautiful one. Even before the melody began, it had me hooked. The melodic arrangement just needs to fill in the gaps and it becomes a good song even if it's just passable. Here it's great so it's a good song to listen to. Electronica like that by Daft Punk is also noted for it's lovely basslines as is Deadmau
The sentry looks out from his tower: "Quo Vadis?"