Position change
Change of the stopping-hand position.
What it means
The position change is the movement of the left hand along the fingerboard from one position into another. It becomes necessary as soon as a melody leaves the stock of notes of one position, and it is at the same time one of the most frequent causes of unclean intonation, because the hand must hit the target in a fast movement. Technically one distinguishes changes on the same finger, changes with a change of finger, and changes by way of an intermediate finger, which as it were prepares the path.
In the notation
A position change becomes visible only indirectly, through the fingering: if the same number is repeated at different pitches, or a high number appears at an unexpected place, a change is present. Some editions place a small line between the two finger numbers to show that the hand travels with a gliding motion.
Musical use
Position changes are not merely technique but a means of expression. An audibly executed change, in which the finger slides on the string, produces a portamento and counts as vocal in character; in Romantic music it is explicitly desired, in Baroque and Classical music to be used rather sparingly. Inaudible changes, by contrast, keep a line smooth. The decision about this belongs to interpretation and is made deliberately, not left to chance.
Performance practice
Practise the change first slowly with the so-called intermediate note: slide with the old finger to the target position, then place the new finger only afterward. In this way the hand learns the distance. The thumb must travel along, otherwise it blocks the movement. During the change, keep the bow pressure stable and avoid reducing it to disguise the shift — this is audible. Where possible, use an open string or a string crossing to cover the change. If intonation is uncertain, check whether the change itself or the target hand shape is the problem, by playing the target spot in isolation.
Bear in mind that the choice between an audible and an inaudible change is a question of style: in Romantic music a vocal slide belongs to the expression, in Baroque and Classical music it seems foreign. Decide deliberately and consistently within one work. Practise changes at first with an intermediate note, so that the hand learns the distance.