Strings for musical instruments seem to be among the simplest of devices. Textbooks on acoustics commonly use them as the most elementary example of a vibrating system. However, the assumptions often made to simplify mathematics are far from the conditions that exist in real strings made of even the most suitable materials available.

Consider what a musician wants in any instrument: as wide a frequency range as practical; considerable acoustic power with a significant difference between loud and soft notes; and, if possible, the ability to play several notes at once. The last requirement dictates the presence of multiple oscillators. Long, thin strings in closely-spaced groups fit the bill, but they are inherently deficient in meeting the other criteria without help from additional devices.

Direct acoustic output from a vibrating string is negligible because it alone cannot move enough air. This deficiency has been corrected in hundreds of ingenious ways over thousands of years by mechanical coupling to a light, stiff structure large enough to radiate the lowest pitch being produced, often incorporating air-cavity resonators tuned to enhance low-frequency output. In this electronic era, unlimited power can be obtained using transducers to detect string motion as electrical voltages that can be amplified and directed to loud-speakers.