Which component is used to flavor a tall mocha frappuccino from the espresso bar?

In a tall mocha frappuccino, the flavor is primarily derived from mocha sauce. This sauce is specifically designed to provide that rich chocolate flavor that defines a mocha beverage. Mocha frappuccinos blend espresso with milk and ice, and the addition of mocha sauce brings depth and sweetness that complements the coffee, making it a popular choice among customers.

The other flavor syrups, such as vanilla, caramel, and hazelnut, contribute their own unique tastes to different beverages or variations, but they are not the key ingredient for the mocha frappuccino. Instead, mocha sauce is essential in creating the signature flavor profile associated with this drink, ensuring it delivers that delightful combination of chocolate and coffee.