Methods and systems of a point of sale controlling system are disclosed. In some aspects, a first musical note tone is assigned to a first checkout system and the first musical note tone is different from a second musical note tone assigned to a second checkout system. Next, in response to a first sound event has occurred for the first checkout system, the first musical note tone is only played for the first checkout system so that the first musical note tone is not played on the second checkout system and the second musical note is not played on the first checkout system.