Any note prod. by an instr. is accompanied by a number of other notes at fixed intervals above it. These are heard as the constituents of the single note, but can be prod. separately. On str. instrs. this is done by touching the string lightly at various points (‘nodes’) so splitting up the vibrations and producing notes of a flute‐like purity (in Ger. and Fr. harmonics are indeed called flageolet). The lowest tone of the harmonic series (the ‘fundamental’) is the 1st harmonic, the next lowest the 2nd harmonic, and so on. Other tones are the ‘upper partials’ or ‘overtones’, at fixed intervals above the fundamental, an octave, then a perfect 5th, etc. On an open str. the result is a ‘natural’ harmonic; on a ‘stopped’ str. (a finger used to stop and another lightly placed) it is an ‘artificial’ harmonic. In brass instrs. harmonics are produced by varying the method of blowing. Every note of normal mus. instr. is a combination of the fundamental and certain upper partials. The only exception is the tuning‐fork.