Prabhupada liked to hum and sing to himself

Satsvarupa Dasa: I've also seen Prabhupada sit in the back seat of a car and crank the window up and down repeatedly, and I have seen him move his finger across a fogged window pane and make playful marks. In a detached way, Prabhupada liked to hum and sing to himself. Whatever Prabhupada did, it was an answer to the question made by Arjuna in the Bhagavad-gita, How does a transcendentalist walk, how does he sit and how does he speak? Sometimes the paramahamsas or swanlike persons float on the water of the material world and appear to be like children. Sometimes they act like madmen and don't communicate at all, although Srila Prabhupada never did that. And most often, they are teachers with their finger raised in the jnana-mudra pose, instructing the conditioned souls.