Variation 2
#spiccato
In variation 2 Ševčík explicitly writes spiccato and M to indicate a bouncing stroke originating from the air near the natural bounce point of the bow, which for most bows will be between the frog and the actual middle point of the bow. Although the M indication suggests a place in the geographical middle of the bow, in many of the variations it will be more beneficial to explore a playing point closer to the frog, where there is more control of the bounce.
Experiment first with trying the bouncing stroke on the open A or open D. To develop a sense of the natural bounce of the bow and string, hold the bow approximately six inches above the string, then allow it to bounce by letting the tip drop freely, while of course maintain a gentle hold on the frog. It is important that you allow gravity and the natural springiness inherent in the qualities of the bow hair and string to do the work. Think of dribbling a basketball or a table tennis ball with a paddle. In those cases, you are not ‘working’ to make it bounce, it is the upper part of the motion that you have control over; once it leaves your hand or paddle, it is up to gravity and the natural bounce characteristics of the surface and the ball.
The spiccato stroke is possible to practice very slowly by exaggerating the distance from the string you are bouncing, as well as the overall movement of the bow. As you speed up, the motions get smaller, as does the bounce. To ‘dial-in’ the ideal bounce, imagine controlling separate knobs for vertical motion and horizontal motion. Depending on the string you are playing on, it may require more horizontal motion to prevent a cracked or strained sound (on the A string) or, conversely, a more vertical motion (on the C string) to ensure enough energy is being put into the thicker string to get it to vibrate.