I haven't seen a single film about homeless people that focuses on the experience of wandering through the city. Most of them focus on the mystery, the story behind the man. The past of this particular person... And that felt very boring to me.
I saw a similar situation once, walking down the street. A homeless man was singing, high as a kite, but not to ask for pennies, he was just expressing himself.
So that felt like the key ingredient I needed to make a story. Exploring the experience of this peculiar musical hobo.