Violin where a stopped note sounds a unison or octave with another (open) string, causing it to resonate sympathetically. Students often use these ringing tones to check the intonation of the stopped note by seeing if it is harmonious with the open string. For example, when playing the stopped pitch "A" on the G string, the violinist could play the open D string at the same time, to check the intonation of the stopped "A". If the "A" is in tune, the "A" and the open D string should produce a harmonious perfect fourth. Violins are tuned in perfect fifths, like
Electric violin to an independent MIDI channel. Most recently, Keith McMillen of Keith McMillen Instruments, a founder of Zeta Music, announced the StringPort polyphonic string-to-USB 2.0 converter for the Zeta polyphonic pickup and other modern polyphonic violin systems. Whilst no other dedicated violin-to-MIDI systems have been manufactured, more generic pitch-to-MIDI systems like those from Roland, and Yamaha can be adapted to use standard electric violin output. Most systems allow only monophonic operation—only one pitch can be detected and digitised at a time—but through the use of proprietary pickups, some limited MIDI polyphony can be achieved. Some pitch to MIDI interfaces from Axon/TerraTec