If the stopping finger is removed from a vibrating string, it interrupts the decay of a tone.
Plucked, struck and bowed sounds are firstly allowed to ring, then their decay is interrupted by removing the stopping finger from the string.
Harmonics work in the opposite way: the decay duration of harmonics is maximised by removing the finger very soon after excitation. In fact, harmonics have an optimum left-hand contact time at which decay duration and overtone content are maximal. This optimal contact time is inversely proportional to the frequency of the harmonic (i.e., longer for lower harmonics). In general, even for low harmonics, this optimal time is very short. For very long contact times, plucked and struck tones become a short, muffled ‘thud’ (in the latter case the clavichord-type pitch is very present). For bowed tones, the harmonic barely sounds after the stroke.
A harmonic is plucked, struck and bowed. At first, the finger is in contact with the string for a short time, then it stays on the string for a longer time, muting the harmonic.
▶︎VERY SHORT CONTACT TIMES AND MULTIPHONICS
Contact times shorter than the optimal time for a particular harmonic encourage a second harmonic or the open string into the sound. Because of this, short contact times can produce multiphonics. This is especially effective for pizzicato multiphonics.
Pizzicato multiphonics produced by short left-hand contact times.
I help encourage the multiphonics by plucking with the very tip of the right-hand finger or the fingernail.
▶︎A NOTE ON BOWING
In some cases, particularly for loud tones, if the finger is removed before the end of the bow stroke, the harmonic continues to sound for a short while. If the speed and tension of the stroke remain constant, this effect can continue for a few seconds.
Bowed harmonics continue to sound even if the finger is removed from the string