The left hand takes no part in the division of the notes, the third finger merely gliding from the highest note of the passage, down to the open A string; the finger should press uniformly on the string, the division of the notes being accomplished by a nervous tremolo movement of the fore-arm which causes the bow to proceed in a series of rapid jerks.
The right hand wrist remains fixed, the pressure on the bow being almost uniform. The above kind of staccato must not be confounded with solid staccato. It is possible to attain a very high rate of speed in a passage as Ex. 51 if executed as explained, but apart from this, the effect is entirely different than if performed with solid staccato, even if it were possible to play the passage as rapidly with the latter form of bowing. Another kind of chromatic passage produced wholly by a bow movement may be found in Davidoff's "Am Springbrunnen" and Popper's "Elfentanz." The following (Ex. 52) is taken from the latter work.
The finger should glide along the string as previously explained, the division of the notes in this instance being accomplished by a rapid spiccato movement of the bow, producing a series of short detached strokes. In a passage of this character it is impossible for either player or listener to discern whether the exact chromatic scale is actually played; the only method to approach anywhere near a faithful interpretation of the passage, is by a correct division of the bow strokes in groups of fours, at the same time carefully regulating the speed of the gliding finger. It will be evident that the gliding must be more rapid when the lower positions of the instrument are reached than in the high positions; thus in commencing the above passage (Ex. 52), the notes being nearer together in the higher positions than in the lower, the hand should move correspondingly slower; the movement becoming more rapid as the passage proceeds.
A third method of producing a chromatic passage—this time, however, with the left hand, without any assistance from the bow for the division of the notes—seems to be a speciality of Servais. It is introduced both in slow portamento effects and rapid chromatic passages.
The bow should be drawn as for a long sustained note, the division of the notes being caused by a series of rapid jerks performed by the left hand. The finger should sustain the pressure on the string during the whole passage, the movement is similar to that explained as the method of producing the vibrato, with the addition of the forward or backward progression of the hand according to the requirements of the passage. The passage may be played with any finger, but it is advisable to use the fourth finger for a descending passage (see Ex. 53) and the first or second finger for an ascending chromatic run. It is also here impossible to attempt to play the real notes except in very slow passages; to execute a rapid chromatic as above, the player should merely grasp the time of the semiquavers, and regulate the distances for each movement previously as explained.
The same effects as above examples are also possible in octaves, they are produced in a similar manner.