There are obvious differences between the mouth flute and the kazoo in terms of structure, playing method, and sound characteristics.

1. Structure: Mouth flutes usually have only one or two mouthpieces, while kazoos have multiple mouthpieces arranged side by side.

2. How to play: The playing of the flute mainly relies on blowing and sucking to produce sound. At the same time, the player needs to control the airflow with the tongue to change the pitch. In contrast, playing the kazoo requires using multiple mouthpieces at the same time, and controlling the airflow and fingering of each mouthpiece to play different notes and melodies.

3. Sound characteristics: The sound of the flute is sharp and bright, and the volume is relatively small. The kazoo has a larger volume, richer and more varied timbre, and can produce more complex musical effects.

To sum up, although the mouth flute and the kazoo are both musical instruments that produce sound by blowing air, they have significant differences in structure, playing method, and sound characteristics.