harmonics explained
Pure, flute-like tones produced on string instruments by lightly touching the string at specific nodal points
In Depth
Natural harmonics are produced by touching the string at fractional divisions (1/2, 1/3, 1/4, etc.) without pressing it to the fingerboard. This isolates specific overtones from the harmonic series, producing ethereal, whistle-like tones. Artificial harmonics are produced by stopping the string normally with one finger and touching it lightly with another a perfect fourth or fifth higher. Harmonics extend the instrument's range upward and create a distinctive tonal colour used for atmospheric and magical effects.
Ravel's orchestration of Mussorgsky's Pictures at an Exhibition uses string harmonics to create the eerie chiming that opens The Old Castle.