Gene Weingarten has an interesting anecdote in the weekend Washington Post on how violinist Joshua Bell’s parents recognized his talent at the very young age of 4:
One biographically intriguing fact about Bell is that he got his first
music lessons when he was a 4-year-old in Bloomington, Ind. His
parents, both psychologists, decided formal training might be a good
idea after they saw that their son had strung rubber bands across his
dresser drawers and was replicating classical tunes by ear, moving
drawers in and out to vary the pitch.