For string teachers, every lesson is a challenge in creative problem solving. Each student comes with unique challenges and we tailor our message to best impact that student, but with experience, common themes emerge. Certain issues recur similarly in many students, and we often repeat certain pieces of advice almost verbatim because we have found them to be true and effective. All teachers have their own recurring themes, and these are a few of mine:
The string is a non-linear system. Like moving a heavy box across the floor, it takes a lot more effort to start it moving than it does to maintain the motion. Misunderstanding this principle can lead to one of two issues: either the student begins the bow with enough pressure to make the string speak but then maintains that same heavy pressure throughout the bow, causing a strangled, crunchy sound (once a string is vibrating, bow speed contributes far more to volume, ring and quality of sound than pressure.) Or, more commonly, they do not apply enough pressure at the start of a stroke, causing the bow to glide over the string, not catching until it has traveled several inches. This first creates a break in the sound and then a 'swelling' effect on each bow stroke, as the string only gradually begins to vibrate, which both interrupt the musical line. We must apply sufficient pressure before the bow stroke begins, but then release much of it as the bow starts to travel (imagine the pre-bowstroke tension as a stretched rubber band, which is released as soon as the bow moves.) Practicing pressing down on a stationary bow, making the stick dip repeatedly towards the hair, and then practicing a series of short, punchy notes on a single up or down bow, with the bow cleanly starting and stopping, often helps this issue. Dropping or vibrating the left hand finger exactly with the attack of the bow also greatly aids in starting the vibration of the string.
Another common problem occurs if a student grows accustomed to bowing close to the fingerboard, where it is easier to play cleanly, and plays even the loudest passages no more than halfway towards the bridge. We often practice in small, reverberant rooms and grow accustomed to a deceptively loud feedback of sound to our ears, even when bowing lightly. Then, when we perform in a larger space, the volume in our ears is suddenly far less than we are used to hearing If we haven't practiced playing closer to the bridge then, under the pressure of performance, we end up simply pressing harder at our usual spot, creating unaccustomed tension and causing intonation and the overall performance to suffer. The sound made playing closer to the bridge is actually a far richer, fuller sound, with more of the instrument ringing, than the sound made playing closer to the fingerboard, no matter how much pressure is applied. We might avoid playing closer to the bridge because it sounds 'dirty', but by playing near the fingerboard, we are not playing more cleanly, only hiding what is not clean (like dimming the lights in your apartment rather than cleaning it!) It is better to practice closer to the bridge than you will actually need to play in performance. If you learn to play cleanly there, you'll know that your coordination is true and, in performance, you can have the comfort of relaxing and doing slightly less than you have practiced rather than trying to do more. Nelsova's characteristic 'long, loud bow' exercises are a fast way to build comfort playing near the bridge. These are simply very long, slow bows played close to the bridge (with a few extra repetitions of each bow change, to practice clean starts of the new bow) As the exercise becomes more comfortable, the bows are played ever slower, and with varying patterns of crescendi and diminuendi. If forced to practice in a small, reverberant space, I also sometimes recommend practicing using clothespins on the bridge or using a portion of a foam earplug.
I find some students suspend their right pinkies in the air, rarely in contact with the bow, and/or they allow their fingers to lose contact with the bow during a whiplash-like bow change motion from an upbow to a downbow. Just as a solid connection of the foot to the floor helps keep your body stable on a lurching subway car, each finger must be able to maintain a point of contact with the bow even as the hand and arm constantly adjust. If the finger/bow contact is lost, bow control is also lost until the connection is re-established. This issue can sometimes be improved by practicing bow strokes holding the bow with only two fingers and thumb at a time (1 and 3, then 1 and 4, then 2 and 4) as this forces a constant connection at the contact point of those fingers. It is also useful to practice bow changes without allowing the hand to shift position on the bow at all. Of course this is not always the most suitable way to change the bow, but if we don't have the control not to move then we can never be in control when we do move. Bow changes are a frequent culprit in breaking the musical line, and each difficult change should be repeated until it is as seamless as possible.
Certain students are unable to move their right hand knuckles flexibly while playing, and are restricted to a single hand position, with their second (middle) knuckles more straight than curled. This is useful for lighter playing, but heavier playing requires the ability to hold the bow with flatter first knuckles (those closest to the back of the hand) and bent second knuckles, in order to better transfer weight to the bow and to play with flatter hair without raising the wrist. No single hand position works for all styles and dynamics, so the hand must be able to shift and the knuckles bend and unbend without ever losing the contact of the fingers with the bow. To develop this, playing the opening of Piatti Caprice #1 very slowly, with the string change made only by the curling and uncurling of the fingers, is useful. If the pinky finger is unable to maintain connection with the bow, it can be placed on the top of the stick until it strengthens enough to maintain contact in the normal position.
I also see many students who play only with the bow rolled towards the fingerboard and are unable to play with the stick directly above the hair -occasionally to the extent that we hear the grind of the bow wood against the string when strong pressure is applied. Again, both types of playing are ultimately needed. Playing with the stick directly above the hair allows more fullness and volume in loud passages and also slows the required bow speed. (Zara Nelsova always advised to roll the stick in our fingers until it was directly above the hair when sustaining long notes. The result would “add several inches to your bow” she promised!) Simply practicing rolling the bow in your fingers as you play long bows, oscillating the stick between angled and directly above the hair (without raising the wrist) can quickly develop a sometimes neglected skill.
An often overlooked idea in the quest for relaxation and balance of the left hand is that the stronger the fingers are, the easier it is to relax. It is not tension that is the enemy, but sustained tension. Feuermann used extensions in a revolutionary way but, watching his hand on film, we see that he never leaves the hand in the extended position for more than an instant, always quickly returning to the relaxed natural spacing. In scales descending the A string, Feuermann recommended having the left hand fingers pluck the strings by pulling off to the side while releasing, in order to build strength. Finger strength is never used to squeeze, but rather only in the initial attack of the note, after which there should always be a subsequent relaxation. It is very important that the left hand fingers are strong enough to articulate very clearly— almost 'knocking' on the fingerboard— particularly in slow playing. In faster passages, the left hand motion should naturally be less articulated and more flowing, but once sufficient strength and independence are developed, it is always easier to do less.
Once we know a piece well, moments of bad intonation are almost always caused by some uncomfortable tension, often tension on the note either directly before or a few notes before the missed note. Left hand tension can cause us to restrict our bow as well, but conversely, we can sometimes relax the left hand in a difficult passage by using our bow more freely. If a note is particularly uncomfortable for me, I force myself to stay on it, vibrating, for a long time (often 30 seconds or more) until I have made whatever adjustments are needed to be comfortable. When we play quickly, we tend to discount moments of tension, but if we stop and “wallow in what is uncomfortable”, our bodies will often find a solution fairly quickly. The body functions well when it moves in fairly continual motion, but less well when moving abruptly from one static position to another, so a slight vibrato or other movement of a finger will make the following note much easier to place. Feeling the agogic rhythmic pulses of the music also helps us relax (in addition to making for better interpretations) because when we lean into the strong rhythmic pulses, we will also naturally relax between them. Playing difficult passages forwards and then backwards helps balance the hand, and I have also found that occasional practice using full bows with almost no bow pressure is great help in freeing up the left hand
Many students are far more comfortable in the lower positions than in thumb position. This is natural, since we usually begin playing in thumb position later and, even then, spend only a fraction of our time there. It is actually easier to play higher than it is to play in the lower positions, but we're less used to it. Unfamiliarity creates tension, discomfort and fear, making it much more intimidating than it should be. Constant exposure is often the quickest cure, with as much work in thumb positions as possible. Scales in doublestops are particularly good practice, as they teach the map of the fingerboard, keep the hand in a simple, natural, efficient hand position and also train the ear to hear intervals more clearly. For etudes, the Greutzmacher, Op. 38 Book 2 are particularly good (once you've played fingered octaves on the cello, regular octaves seem relaxing in comparison!) and they are also useful for their repeated use of the fourth finger in thumb position. This both strengthens the fourth finger and also keeps the hand from becoming overly angled away from the line of the strings. Too much angle in the higher registers hinders facility and causes the vibrato to travel more diagonally across the string, making it nearly impossible to vary the color and intensity sufficiently.
I believe vibrato is perhaps the least addressed aspect of our art today. Many otherwise excellent players are not able to produce enough variety of vibrato speeds and widths to express the music adequately. Vibrato is sometimes treated almost as an afterthought- either present or not- but it is actually one of our most crucial tools for shaping the sound and the phrase. People often speak wistfully of being able to identify players of the golden age after hearing 'just a few notes'; I believe the primary reason for this was their very personal use of vibrato, and that the accompanying complaint that many modern players 'sound the same' stems in part from a lack of variety in their approach to vibrato.
Vibrato, used properly, should be motion that relaxes the hand. As with the bow, most of the energy is spent starting the motion, after which it can be maintained with much less effort. Force is required to roll the finger forward, but then it naturally falls back and and settles into a comfortable oscillation (I've never understood arguments about vibrating 'around the pitch' vs. 'under the pitch'. Vibrato is oscillation- by definition, motion above and below a median point. Those arguments seem to be simply about what point in the oscillation one defines as the 'pitch') Since starting the motion is the difficulty, practicing repeatedly starting vibrato on a note and then letting it naturally die off, during a long, sustained bow, can be very effective in uncoupling the vibrato motion from the right hand (be careful that the bow doesn't diminuendo as the vibrato motion fades.) If a student doesn't relax somewhat after the start of the vibrato and instead drives the vibrato all the way through the note with constant physical effort, it produces an unpleasantly forced, driven sound and the vibrato will then become a source of tension rather than relaxation.
Another problem seen even in some top-level players is the habit of regularly not vibrating the beginnings of notes. Not only does the rigid start to each note create tension in the hand, but more importantly the delayed vibrato creates swells on almost every note, destroying the possibility of a longer phrase line. Consciously trying to vibrate on every single note often ends up making the phrase sound homogenized, but if the student instead focuses on producing beautiful vibrato in the places of musical tension (melodic, harmonic or rhythmic) and simply relaxes between, there is usually enough residual hand motion and freedom to leave the connecting notes with enough vibrato. It isn't about producing mountains of vibrato everywhere; sometimes even the just faintest hint of vibrato on a note (“half a wiggle”) changes the sound from rough to polished.
Our natural vibrato is usually best with the 2nd and 3rd fingers, as the weight of the hand is most evenly distributed. For the 1st, and particularly the 4th finger, it is easier if the hand rotates slightly towards the finger and the other fingers close together, bringing the center of mass of the hand closer to the point of oscillation. Some students find their 4th finger curling up towards the palm when vibrating their 3rd finger. This is an artifact of the hand tension, and often destructive as it distorts the vibrato and creates even more tension. Better to brace the 4th finger against the 3rd when vibrating the 3rd . Generally when more fingers are brought together so that the hand vibrates more as a block, the vibrato is wider and rounder, while vibrato that is made more by just a single finger is narrower and more intense.
Feuermann made his students sustain a single note, switching from finger to finger trying to match the sound of the vibrato on each finger (including the thumb!) I also find it useful to have students practice vibrating each finger, starting exaggeratedly slow and wide, then speeding and narrowing through the entire spectrum to exaggeratedly fast and tight, and back again to slow. Remember that the ideal vibrato speed varies not just with the content of the music, but also by the register of the cello, and we need a full palette of colors available for every note. String players are essentially singers and our first priority has to be to produce enticingly beautiful sound. If the sound isn't gorgeous, it will matter little to the audience what else we have to say. Far too often, students settle too easily for whatever vibrato they can manage; we must take responsibility for the beauty of our sound and never settle for simply 'OK'.
Though cellists spend a lot of time discussing the ergonomics of shifting, I often find that students don't spend enough time actually practicing shifting, which is the fastest and most practical way to gain comfort. Not many etude books emphasize this adequately, but it's easy enough to make up your own exercises, repeating shifts with different fingerings, bowings and intervals, including fifths, octaves, 12ths and double octaves. Shifting in double stops is particularly useful. It is important that both the departure and arrival note can be played comfortably, and I find holding and vibrating them until each is relaxed and comfortable to be very helpful. Often when a shift is missed, it is because the bow has rushed the left hand – try waiting longer with the bow, or using less bow.
Using shifts to produce artful glissandi is another very personal and somewhat lost art of the golden age. Just as with singers, a natural sounding ascending glissando is only really be audible in the top part of the slide (otherwise, it may sound like a passing race car.) The descending glissando will also only emphasize the top (departure) region, else it may sound rather like an unhappy cow. Glissandi should be connective tissue that adds musical emphasis to the arrival or departure note, not musical events unto themselves.
Trying to give interpretive advice in broad terms is nearly impossible; it takes years of experience to develop the musical imagination, but a goal that eludes many students is to be able to play simple, long lines, free from any extraneous accents, swells and separations. These are often unintended consequences of technical issues and they prevent us from hearing the true nature of the longer musical line. There is nothing more difficult in music than to be simple, but it is when we are able to play simply, without extraneous distraction from the longer line, that our personal musical interpretations are most beautiful. I sometimes find it is helpful to play a phrase considerably faster than concert tempo, in order to better understand the long line, and then try to slow it down without disturbing that line.
A few other words of general advice. Many students practice inefficiently, devoting far too much time to playing through what they can already do well and, in the brief moments when they do repeat what went wrong, they are often satisfied with only a single correction before going on. Doing that, they have trained their brain once incorrectly and once correctly, which should yield around a 50% chance of getting it right the next time. Students almost always underestimate the number of times something must be repeated correctly to train our brains reliably, but by zeroing in on exactly what they can not do well and practicing it repeatedly until it is comfortable and reliable, they will ultimately save countless hours of practice time. I have also found that it is much easier to break undesirable habits by first exaggerating the opposite extreme and then easing back, rather than trying to slightly modify what I was doing. As with playing near the bridge, once an extreme is practiced, it is usually comfortable and easy to do less.
Ultimately all words of advice are of limited use. Real learning begins when students can truly hear what they want in their minds and can also honestly and accurately hear what they actually produce on the cello. If students are capable of those two things, they will quickly be able to discover their own issues and find their own solutions. Playing the cello is a lifelong journey of discovery, frustration and love but, to paraphrase Rachmaninoff, while a lifetime is not enough to learn all there is to playing the cello, the cello is enough for a lifetime.