Modulus Guitars. Modulus Graphite (formerly, Modulus Guitars) is an American manufacturer of musical instruments best known for building bass guitars with carbon fiber necks. The company, originally called Modulus Graphite, was founded in part by Geoff Gould, a bassist who also worked for an aerospace company in Palo Alto, California, and coworker Jerry Dorsch. When they split, Jerry started Graphite Guitar Systems in Washington state.

History 
The name is a reference to Young's modulus, a measure of the stiffness of an elastic material, used in the field of solid mechanics. Carbon fiber has an exceptionally high modulus.

Traditionally, electric guitar and bass necks are made from hardwoods (such as maple or mahogany) reinforced with an adjustable steel "truss rod."  Wood, being a naturally occurring material, is prone to variations in density and flexibility. This, coupled with the high stresses created by stretching steel strings across them lengthwise, makes wood necks prone to certain unpredictable and undesirable qualities. Among these are twisting, incorrect "bowing" (either too pronounced or too subtle), and "dead spots," or areas on the neck where notes are quieter or more indistinct compared to other areas. Non-traditional neck materials such as carbon fiber and aluminum are attempts to correct these issues by replacing wood with lighter, stiffer and more uniform components.

Gould was inspired to experiment with non-traditional materials after attending a 1974 Grateful Dead concert, at which he marveled at the size and complexity of Phil Lesh's heavily modified bass (customized by Alembic) and began to consider the possibilities of lighter, stronger materials. After being passed over by his employers in the aerospace industry, the project of creating hollow, carbon fiber bass necks was brought to fruition by Gould and Alembic, who built a bass with a prototype neck and displayed it at a trade show in 1977. Immediately after the trade show, the bass was purchased by Fleetwood Mac bassist John McVie.

Gould and some of his colleagues in the aerospace industry founded Modulus Graphite and began to make necks for Alembic and other companies before moving on to making entire instruments.
Geoff Gould left the company in 1996 to form G. Gould instruments

December 20, 2013 Modulus Guitars LLC was placed into voluntary Chapter 7 arrangements.

Instruments 
SP and SPX (bolt-on and neck-through models) 
BaSSStar - Mostly available as a replacement neck, but some were built as whole instruments(both bolt-on and neck-through models, some headed and headless necks were also available) 
Flight 4 (Headless 4 string basses with the shape of a Space Rocket, Maybe 10-15 known to be built)
Monocoque (Headless bass with a 1 piece body and neck all from carbon fiber)
TBX (through body experimental); it is rumoured, that only 11 four-string, 85 five-string and 90 6-string basses were made before year 2000 - production has started again 
Quantum SPi bass (SPi = integrated, bolt-on neck; basic version has two EMG pickups, custom options include exotic wood tops and electronics;  5-string has 17, 19 or 21.5 mm bridge spacing options) 
M-92 (Sweet Spot bass = single EMG pick up, bolt-on neck, pickguard; in production since 1992, Turbo model added a second pickup next to the bridge; 4, 5 and 6 string models,)
Sonic Hammer (like M-92, but bartolini pick-up and electronics, quilt top, no pickguard) 
Genesis Bass (bolt-on neck with carbon core, wood sides and fretboard; co-designed with Michael Tobias) 
Modulus VJ Bass (Vintage J, bolt-on, active or passive electronics) 
Funk Unlimited (formerly Sonic Hammer and the Flea Bass, bolt-on neck; also available as chambered & lightweight RevOLite version) 
Funk Persuasion (single pick up, passive electronics, bolt-on neck; also available as chambered & lightweight RevOLite version) 
Vertex (single pick-up, bolt-on)

Formerly 
Modulus Genesis I Electric Guitar (G1)
Modulus Genesis I Electric Guitar with tremolo (G1T)
Modulus Genesis II Electric Guitar (G2)
Modulus Genesis II Electric Guitar with tremolo (G2T)
Modulus Genesis III Electric Guitar (G3)
Modulus Genesis III Electric Guitar (G3T)
Modulus Genesis III Electric Guitar Carved Top (G3CT)
Modulus Genesis III Electric Guitar Semi Hollow (G3SH)
Modulus Genesis III Electric Guitar Full Hollow (G3FH)

Notable players 

Musicians that play/have played Modulus instruments are:

Steve Rodby - Pat Metheny
David Ellefson - Megadeth
Flea - Red Hot Chili Peppers
Phil Lesh - Grateful Dead
Darryl Jenifer - Bad Brains
Bob Weir - Grateful Dead
Jack Casady - Jefferson Airplane - Hot Tuna
Oteil Burbridge - Allman Brothers Band
Stefan Lessard - Dave Matthews Band
Me'shell Ndegeocello 
Mike Gordon - Phish
Dave Schools - Widespread Panic  
Jeff Ament - Pearl Jam
Pete Sears - Rod Stewart - Long John Baldry - Jefferson Starship - David Nelson Band
Chad Urmston and Pete Francis Heimbold - Dispatch
Alex Webster - Cannibal Corpse - Hate Eternal
Wil-Dog Abers - Ozomatli
Futoshi Uehara - Maximum the Hormone
Tad Kinchla - Blues Traveler
Alphonso Johnson
Divinity Roxx
Christopher Rapkin

References

External links
 Official website

Guitar manufacturing companies of the United States