The cellist can influence the overtone content, loudness and duration of string’s vibration depending on where, how and with what it is plucked, struck and bowed.
TERMINOLOGY AND DEFINITIONS
GENERAL DEFINITIONS FOR ‘PLUCKING’, ‘STRIKING’ AND ‘BOWING’ A STRING.
Cello map considers all the possibilities of generating sound in a cello and does not prioritize classical techniques. Therefore, it is necessary to consider ‘plucking’, ‘striking’ and ‘bowing’ a string in more general terms than cellists are used to.
I use the terms ‘plectrum’, ‘hammer’ and ‘bowing object’ to describe any objects that make the string vibrate by plucking/striking or bowing. For example, a plectrum could be a finger or a credit card; a hammer could be the bow stick or a pencil; a bowing object could be the bow hair or the bow stick drawn across the string… Since all of these objects ‘excite’ vibration in the string I will use the even more general term ‘exciter’ when information applies to a plectrum, hammer or bow.
The following descriptions of the actions of plucking, striking and bowing a string provide a basis for some of the information in this resource.
▶︎DEFINITION OF PLUCKING
A plectrum pulls the string, and, upon releasing it, sends two kinks of vibration from the contact point, one in the direction of the bridge and the other in the direction of the nut. The kinks are reflected at the bridge/nut or, in the case of a stopped string, at the stopping finger. This process continues until the excitation energy runs out.
▶︎DEFINITION OF STRIKING
A hammer strikes the string. Two systems of vibration take place:
1. Firstly, kinks of vibration are sent from the hammer to the bridge and from the hammer to the nut. This vibration is reflected between bridge-hammer and nut-hammer. The portion of string under the hammer does not vibrate. This continues as long as the hammer is in contact with the string (or until the excitation energy is used up). I refer to this as ‘clavichord-type’ vibration because it is similar to the mechanism of a clavichord.
In the case of an open string, two pitches are heard, the ‘hammer-to-bridge’ pitch and the ‘hammer-to-nut’ pitch. For a stopped string, the string vibrates hammer-bridge and hammer-stopping finger. Because the string length ‘hammer-stopping finger’ it is not in contact with the cello body (vibration can not travel through the bridge or the nut), it is not well amplified, therefore, usually quiet and sometimes inaudible.
2. Secondly, as the hammer leaves the string (often, the hammer is ‘thrown’ from the string after impact), the vibration is able to travel across the section of the string that was previously under the hammer. Vibration is reflected between the bridge and nut /stopping finger. Vibration continues until the excitation energy is used up. The resulting pitch is that associated with the length of string from nut/stopping finger to bridge. I will refer to this as ‘piano-type’ vibration because it is similar to the mechanism of a piano. This tone is traditionally the notated pitch and it is usually the most prominent within the sound, unless the stopped pitch is particularly high. Although piano battuto takes place after clavichord battuto, the two sounds are usually perceived as simultaneous.
The term Col legno battuto implies striking a string with the bow stick and the notated pitch is the piano-type tone. The hammer-bridge pitches of clavichord-type vibration are often called legno battuto saltando. This usually implies isolating the hammer-bridge pitches by damping the string between hammer and nut.
The bow is placed on the string and the string is plucked either side of the bow to show the clavichord-type pitches. Then, the bow is held to the string after striking; the clavichord-pitches sound. Finally, the bow strikes the string; the piano-type pitch is dominant. This is shown for an open and stopped string.
▶︎DEFINITION OF BOWING
The bow is drawn across the string. Vibration is caused by a repeating cycle of excitation: initially the string ‘sticks’ to the bow and moves with it, sending a kink of vibration to the bridge, where it is reflected. The tension of the stretched string increases and as the kink of the displaced string returns to the bow, the string breaks free from the bow and ‘slips’ back to its rest position. This is known as the ‘stick-slip’ process.
When the bow is used in the traditional way, a cellist can influence the sound by changing three elements: bow speed, point of contact and bow pressure. These three properties are dependent upon one another. One way to view this relationship is that the ‘optimum’ and maximal/minimal bow speed and pressure vary for each contact point. In other words, for every contact point there is a band of values within which a ‘normal’ arco sound can be produced. Furthermore, for every fixed point of contact, a change in bow speed is also a relative change in bow pressure. Outside this band of ‘normal’ sound there are areas of over- and under-pressure which can be controlled and quite specifically described.
When the bow is removed from the string, the string vibration decays until the excitation energy is used up unless the vibration is dampened, for example, by removing the stopping finger from the string.
Drawing an object across a string does not necessarily produce this kind of vibration. The properties of the bow hair and the stickiness of the rosin mean that the ‘usual’ way of bowing the string is particularly reliable and flexible. However, for example, drawing the wood of the bow across the string might create some slip-stick vibration but this might be less noticeable than the noise of the wood of the bow rubbing against the strings. The ‘noise’ of the bow hair rubbing against the strings is present in traditional bowed sound. It can be particularly noticeable for quiet tones and high pitches. The quality and the relationship between noise and slip-stick vibration changes depending on the type of bowing object used. Applying rosin can improve the object’s ability to stick to the string and promote slip-stick vibration. The parameters of bow speed/pressure/contact point vary depending on the quality of the bowing object.
Traditionally, drawing the bow hair across the string is described as con crini tratto, although this term is usually only used to cancel a preceding technique that uses the bow stick or another object. Bowing with the bow stick is termed col legno tratto.