No. 30.
As a preparation for this étude, use the Schradieck and Sevcik works. I find Schradieck’s Technical Exercises and Scales and Arpeggios valuable, though I prefer the method of playing scales as advocated by Halir, because Schradieck repeats the fundamental note, thereby making a perfect legato well-nigh impossible. The order of Schradieck’s scales I do not deprecate. The stroke here used is a short staccato in the upper third or a martelé in the middle of the bow. I have already explained how to cross one string without playing upon it. Throw the bow by a short quick stroke of the forearm well over the string, keeping the arm high, out from the body. Make a curve, not an angle.
If the very high positions and rapid changes seem too difficult, play the intervals on the piano a few times. Think the tone. Do not strive for speed. The bowing and intonation are of first importance. Play the slurred notes in the sixth, seventh, eighth, and ninth lines legato, until freedom is secured. Altogether this is a most difficult étude, and it should be practiced even when other études are under our consideration.
The entire étude is not played with a very short staccato stroke. The fingers must seek their positions at once. Avoid an awkward arm stroke.