The artist explains how he varies the attock and timbre of a note by modifying the angle of the bow to the string
Like singers or speakers forming words, string players have the ability to define the type of articulation we choose for each bow change. The principle behind bowing is, of course, pulling and pushing: we pull the down bow and push the up bow, but this can only work if the angle for a down bow is different to that of an up bow. Perhaps this is obvious, but most players have only a casual or superficial knowledge of their bow's relative angle at any given moment - except during string-crossing passages where we have to be conscious and precise. I would like to explore the musical and tonal ramifications of the bow's angle.
The basis of the concept is that of resistance. Let us begin with a broad stroke on the D string. I position the bow at the frog and pull the down bow at an angle close to the A string, so that the D string bends toward the G string rather than being pressed down from above towards the instrument's belly. On the up bow I lower the level of my right arm so that the angle of the bow is nearer the G string and I push the D string towards the A string in both strokes, paying attention to the core of the sound and the feeling of weight and resistance. This simple manoeuvre increases the resistance I feel from the string. The opposite angle, which results in a feeling of less weight and resistance, will produce an airy, silkier sound, yet equally valid when used appropriately.
When using this technique correctly the right arm will make a circular motion - the key to fluidity and tension-free playing. If I want a sound with maximum core then the arm should form a clockwise circle (as seen by the player), whereas for the lighter, more 'French' sound, the arm motion is anticlockwise. The shape is controlled by your wrist and can be circular or more like a see-saw, depending on the type of bow change.
In speech or song, if there is a consonant at the beginning of a word, we must do something with the lips and tongue to annunciate. I try to emulate this on the cello by varying the angle of the stroke, depending on what kind of consonant or vowel is desired. For instance, for a hard sound, such as a 'T' (sforzando down bow), I begin with the bow angled towards the higher string, for maximum resistance, then add arm weight and pull the bow quickly. For a succession of consonants I adjust the angle of the bow before each bow change.
Now let us assume that I want the more powerful, concentrated sound beginning with a soft, vowel-type articulation. On a down bow I position the bow close to the lower string, which speaks more easily because of less resistance, then the moment it responds I raise my arm so the bow is closer to the upper string. To change to the up bow I raise my arm even higher, then settle back down close to the lower string again, creating maximum resistance at the change. The results are a sound with real core and seamless bow changes without a fight to get the string to speak. If, on the other hand, a vowel-type bow change and light tone is required, as in a soft, tender passage, then the arm would remain in the same position.
Let's look at the opening theme of the Cello Sonata no.1 in E minor by Brahms, as an example. I begin at the angle of low resistance so that the first note speaks immediately. There are three or four notes that I wish to bring out because they have dissonance with the piano, representing points of tension or pain - the first is the C in bar two, which falls on the down bow. I slightly elevate my right arm, add a little weight and bow speed, and feel resistance. The result is a wistful sigh formed by the falling second. The next note is the F sharp in bar four, with its suggested modulation and added intensity. The previous note (E) was a down bow, so I lower my arm for the up bow, thus pushing the C string towards the G string for the added tension. I would follow the same procedure for the high F sharp in bar six, the G, and particularly the F sharp in the next bar. Listen critically to develop a real core to the sound in these few notes and the shape of the phrase will be immediately apparent.
We can further apply this technique in a semi-quaver passage. Usually players go back and forth in one plane and will either sound ponticello or scrubby, because there is too much resistance. Let us imagine the passage is all on the D string. The down bow should be close to the G string and the up bow close to the A string. When the passage is fast the circle is made with the wrist. This is perfect for Bach, but would work equally well for a continuous quaver passage like the one (bar 178) in the first movement of Shostakovich's Cello Concerto no.1 op107. Of course, you must be in the right part of the bow and I must emphasise that the contact should remain the same throughout.
In the case of Baroque music, such as the Courante from Bach's Second Suite or the Prelude of the Third Suite, I recommend Playing nearer the fingerboard as this will better replicate the feeling and sound of gut strings. Even though you are on the fingerboard, make sure the bow's contact with the string is firm or the tone will be pale. It is helpful in this bow stroke to feel more in the string during the downbow, as you navigate the low part of the circle.
Finally, this technique will work equally well in lighter spiccato or heavy, slower, off-the-string strokes as well as for accents and sforzandos - the same principles apply.