Violin is a natural sign. Take your non-dominant hand, hold it up in a fist, and lift your entire arm with a slight crook at the elbow, to mimic holding the violin up on your shoulder. Then take your dominant hand and form it into a modified ASL letter X sign as you pretend to play the bow over the violin strings.
Remember to also tilt your head to the shoulder side where the violin is resting. This is to mimic a real violinist's complete actions.
Teach your baby or toddler the violin if your family is inclined to watch violin concertos live or on screen. You can also teach this sign if your little one sees their storybook character playing this instrument.
It is great to teach your child the musical instrument flash cards early on, particularly if you belong to a musical family and would like to introduce your child early to their hobby possibilities.