That description matches a parade , and more specifically a festival parade or carnival parade.

What it is

A parade is a procession of people moving along a street, usually organized with marching bands, floats, and often people in costumes. Carnival-style parades are a common type of festival parade where costumed participants, music, and decorated floats move through city streets as part of a larger celebration.

Why it fits your clues

• Bands: Marching bands or musical groups commonly lead or accompany parades.

• People wearing costumes: Many festival or carnival parades feature elaborate costumes and masks.

• Floats marching down the street: Decorated floats moving along a street route are a defining feature of many parades.