It is not a universal solution, even for the very tallented, unfortunately. As you all may remember our homeless brother in hospital for throat cancer, Vinny, who I wrote about, and you all sent lovely cards to at Christmas. Vin is a GREAT harmonica player, but just not a busker. I often give him a harmonica, when I can. He plays it for his pals, but never busks - and in a few days, gets drunk and forgets where he left it.
As far as tin whistles... NO!!! Unless the folks know how to play them, there is no better way to make sure some NYC cop will crack a homeless bloke in the head, then if he or she is making some high pitched racket. There is little worse than the sound of someone tootleing on a whistle who does not know how to play it. Harmonica's are much more forgiving.
Be careful of good ideas!
Larry