Ta-da is the phrase you say when you show the conclusion of a trick or a surprise. It is believed to be based on the sound of two notes (e.g. bells, piano notes) one would play at the conclusion of a trick. For example: Magician: Think of a number from 1 to 10 and I will guess it. Person: Ok. Magician: You are thinking of the number 3. Person: Yes, I was! Magician: Ta-da!