17Firstly, there is no agreement between the parties, since the passers-by voluntarily make a donation, whose amount they determine as they wish. Secondly, there is no necessary link between the musical service and the payments to which it gives rise. The passers-by do not request music to be played for them; moreover, they pay sums which depend not on the musical service but on subjective motives which may bring feelings of sympathy into play. Indeed some persons place money, sometimes a considerable sum, in the musician's collecting tin without lingering, whereas others listen to the music for some time without making any donation at all.