A small and/or dense plectrum/hammer/bow produces a brighter sound with more overtones.

A string is plucked with the finger and then a credit card and struck with the wood of the bow and then a knife. Overtone-richer sounds are produced by the smaller, denser objects.


A special case, using two plectra

Plucking with a plectrum of a particular width is almost equivalent to using two plectra with outer edges separated by that width.  For example, plucking with two widely spread fingers in the same or opposite directions can reduce overtones significantly.

An overtone-weak sound is produced by plucking with two widely spaced fingers. Firstly, two fingers from the right hand and then one finger from the left hand and one from the right. The sound is equivalent to a (much less practicable) plectrum of the width between the outer edges of the fingers. I dampen the other strings with my chin.

The sound produced by two plectra is also louder.  When two or more plectra are used, the string vibrates with the combined amplitude associated with the excitation force of each plectrum. 


Changing the width and density of the hammer affects piano- and clavichord-type vibration differently.  

The contact area and the contact time between hammer and string are influenced.

Thin and/or dense hammers result in overtone-rich piano-type battuti.  This effect is enhanced since thin, dense hammers, as well as reducing contact area, also reduce contact time between hammer and string, allowing the piano-type vibration to ring for longer with a more overtone-rich spectrum.  

Wide and/or soft hammers increase the contact time between hammer and string.  This favours clavichord-type vibration.  For wide, high-density hammers, clavichord-type battuto is long and overtone-rich.  However, if the hammer is very soft, both piano- and clavichord-type vibration are significantly muted.

Hammer width also influences the pitch of clavichord-type tones.  The portion of string under the hammer does not vibrate (until after the hammer is released, i.e., in piano-type vibration).  The two clavichord-type pitches are equal when the mid point of the hammer is in line with the mid point of the string.  Therefore, for a wide hammer this ‘mid-point-pitch’ is higher than for a small hammer.  

Fingerschlag/hammer on/finger tapping

The stopping finger can be used as a hammer by placing it onto the fingerboard with a force that causes the string to vibrate.  The string responds in clavichord-type vibration.  Two pitches are produced as the lengths of string between bridge-edge of stopping finger and bridge, and nut-edge of stopping finger and nut vibrate.  

The longer string length (lower pitch) is usually louder.  However, the finger-to-bridge pitch is slightly favoured over the finger-nut pitch.  Therefore: at the mid point, the finger-to-bridge sound is slightly louder, and: the two pitches are equally loud just above the mid point of the string (towards the bridge).  

The harder the attack, the longer the decay time, richer the overtone content and louder the sound.  However, at moderate attacking forces these increases quickly plateau and the ‘noise’ of the contact between finger and fingerboard becomes more noticeable than the pitch of the sound.  Using a dense object, e.g., the fingernail, rather than the finger pad, enriches overtone content and lengthens the decay of the tone.  As long as the finger remains in contact with the fingerboard, the sound decays naturally, otherwise it stops as the finger is removed.  If the string is dampened or stopped on one side of the finger, a single pitch is isolated. 

A glissando Fingerschlag with a long decay: the fingernail is used to stop the string.

Using the fingernail to stop the string with fairly high pressure increases the length of the decay of a glissando Fingerschlag. However, it is difficult to accurately control intonation using the fingernail because the angle of the hand is different from the usual position.


The word ‘hammer on’ comes from guitarists’ terminology.  Guitarists usually pluck a string before a hammer on so it is already vibrating when the finger stops the string.  A ‘pull off’, which often follows the ‘hammer on’, is a left hand pizzicato executed by the hammering finger as it is removed from the string. 

Three examples of guitar-style hammer ons (played slowly and then fast)


Changing bow width is possible by using a violin or double bass bow or tilting the cello bow so fewer hairs are in contact with the string.  In general, thin bows produce a more overtone-rich sound.   However, the differences in weight, length and distribution of pressure limit the dynamic range.  

Bowing with the bow stick: col legno tratto

Drawing the wood of the bow across the string, col legno tratto, produces a ‘noisy’, pitched sound.  The tone is unstable as vibration stops and restarts during the stroke.  Vibration is more consistent if the strings and/or the wood of the bow have a layer of rosin on them.  

The timbre of the wood-against-strings sound changes with bow speed and pressure:  -For fast, light bow strokes, there is very little pitch content and the character is a smooth, high-pitched ‘sweeping’ sound.  

-For relatively light, slower bow strokes, lower pitches are present and the bow stick rattles slightly against the string.  

-Under high bow pressures and for slow bow strokes the sound is deep and ‘grainy’ (like a buzzing loudspeaker).  As pressure increases, the bow might be able to grip the string in the usual way for a short while and produce a relatively ‘normal’-sounding arco tone.

The pitches from bow to bridge/nut might also be faintly heard.

Some examples of col legno tratto: a ‘sweeping’ sound with a fast, light stroke; a pitched rattle for a slower, light stroke; a ‘grainy’ sound for a mid/high-pressure, slow stroke, a ‘normale’ sound for a heavy, medium-fast stroke. The different sounds are shown for the open string and for the string dampened with the left hand. The string between the bow and the bridge/nut also vibrates. I show this at the end of the video by sweeping the bow up and down the length of the string; a faint glissando is heard.

The bow stick can be substituted with other objects.  If these tratto objects are shiny/slippery, they are less able to grip the string and generate mostly ‘sweeping’ noise with high pitch-band content.  Rougher objects grip the string more successfully and produce lower-pitched sounds, often with a rattle and occasional ‘normal’-sounding bowed tones.

Examples of tratto with a shiny object and serrated knife.

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