What is the proper thumb positioning for bow handling on the violin and viola?

The correct choice emphasizes that a rounded thumb with the pinky on top of the bow is essential for proper bow handling technique on the violin and viola. This positioning allows for maximum flexibility and control, enabling the player to adjust the pressure and angle of the bow as needed. When the thumb is rounded, it can help maintain a natural grip that supports smooth bow strokes and facilitates a stable yet fluid motion while playing.

Furthermore, placing the pinky on top of the bow enhances balance and allows for better articulation while performing various techniques, such as legato or staccato. This proper thumb positioning is crucial for developing good habits early on in string instrument playing, leading to more effective practice and better overall performance. Being mindful of hand shape and finger placement can significantly influence a player's ability to produce a clean, focused sound from their instrument.