Let's start by saying that "tone" is a group of things. It starts by making a string vibrate. The strings will vibrate differently depending on: 1- Your hands - Where do you pluck the strings, how hard, at what angle. Where do you press the note with your left hand (close to fret, not so close), how hard you press, any vibrato, etc. 2- Action - Higher or lower action will modify a lot how strings vibrate, how they "interface" with the body, neck, frets (buzz, no buzz), etc. 3- The string itself. Is it nickel? Stainless Still? Something else? Rounds? Flats? Something else? 4- Bass construction - Here it is a combination of types of wood, bass design, neck joint, and it has to do with resonance. The bass construction will resonate better on some frequencies and not so good in other frequencies. This will change how strings vibrate. The effect is not as pronounced as in acoustic instruments. Then this vibration needs to be converted to electric signal: 5- Pickups. In a simple way, pickups are "magnets" that pick up (duh) string vibration and transform in an electrical signal. What pickup (single coil, humbucking), how many, where it is located, how it is wounded will make difference on how the string vibration will be converted to an electric signal. 6- Internal "Eqing" - Some basses are passive, some basses are active. Passive basses have usually a passive tone control that removes high frequencies. Active basses have an internal preamp that can boost overall signal or boost or cut certain frequencies. Since this is the Basses thread, I won't go into other aspects (cables, effects, amplification). Please share your ideas! Is there something missing? Do you disagree with something? Why? Would you like to go into more detail on a single item?