Bass Guitar

Overview

A bass guitar is the low-pitched member of the electric guitar family, tuned an octave below the bottom four strings of a guitar. It anchors the harmony and rhythm of a band by sounding the root notes a listener feels more than hears. Unlike an acoustic instrument it makes almost no sound by itself; the body is a solid plank and the strings are too heavy to project. Instead the vibration of its steel strings is sensed electromagnetically and sent to an amplifier, so the real instrument is the pickup-and-string system mounted on a stable wooden platform.

The two structural pieces are the Body and the bolt-on Neck, joined at a routed pocket. Four Bass Strings run from the Tuning Machine set at the headstock, across the Nut and Frets, to the Bridge. Two Magnetic Pickups sit under the strings and feed the Control Assembly.

How it works

Pitch comes from string length and tension. A player tunes each string with its Tuning Machine, a worm-gear set whose high ratio lets fine, stable adjustments, and shortens the vibrating length by pressing the string against a Fret. The frets are wire crowns set at exact positions so each stopped note lands in tune. The Truss Rod inside the neck is the part that makes all this playable: string tension would bow a wooden neck forward, so the rod is tightened to pull it back into a slight, even relief. The Bridge saddles set each string's exact length, so the fretted notes stay in tune up the neck, and its height.

Sound is generated by the Magnetic Pickup. Each pickup is a coil of fine copper wire wound around magnetic pole pieces; the magnets magnetise the steel string above them. When the string vibrates it disturbs that magnetic field, and a changing field through a coil induces a voltage, so the coil outputs a small electrical copy of the string's motion. The neck pickup hears more of the string's fundamental for a round tone; the bridge pickup hears more upper harmonics for a brighter, growling tone. Their signals run into the Control Assembly, where volume potentiometers set the blend and a tone control bleeds treble to ground through a capacitor before the combined signal leaves through the output jack to an amplifier.