The four strings on a violin are tuned in fifths, making it essential for violinists to press two strings simultaneously with the same finger to play a perfect fifth (except on open strings).
However, using one finger to play two strings at once is quite challenging, as the fingertip’s contact area with the fingerboard is not wide enough to cover both strings.
Faced with a perfect fifth, a violinist might be tempted to roll their hand beneath the violin, covering both notes with a flat finger. Nevertheless, playing with flat fingers causes tension in the left hand for several reasons. Firstly, more pressure is needed to depress the string because a flat finger exerts less weight per square inch on the fingerboard than one standing on its tip. Secondly, the wrist must uncomfortably deviate to the left instead of remaining straight. Lastly, moving the hand away from and back to its ideal position takes time, which can make the player feel rushed and lead to them squeezing their hand against the fingerboard. Often, violinists continue to play with flattened fingers even after the perfect fifth has passed, as tension causes the hand to press against the underside of the fingerboard and not release easily.
So, how should a violinist play a perfect fifth without using a flat finger? It’s best to find a fingertip position between both strings that catches both simultaneously. Since each student’s hand and finger shape is different, it’s usually necessary to experiment to find the optimal placement for each finger. In any case, it’s preferable to produce a slightly imperfect fifth rather than altering the entire hand position to accommodate this interval.