A neck assembly for a string instrument and the resulting string instrument. Resin reinforced fibers are shaped into the form of an instrument neck around a tubular structure. The tubular structure creates conduits within the neck. The conduits interconnect, thereby forming a single resonance chamber. The presence of the conduits decreases the weight of the neck. The result is a synthetic instrument neck that has a weight and acoustical properties comparable to a traditional wooden neck. The synthetic neck may also contains at least one mounting plate that enables the synthetic neck to be connected to many preexisting instrument bodies and tuning key heads. The synthetic instrument neck can therefore be retroactively added to existing instruments without the need for alterations.