a dholak, the stretched membrane vibrates to produce sound. In a sitar, the stretched strings vibrate. In a flute, the air column inside vibrates.
Detailed Explanation:
Dholak:
The dholak is a percussion instrument with a drum-like sound. When the membranes are struck, they vibrate, causing the sound.
Sitar:
The sitar is a stringed instrument. When the strings are plucked, they vibrate, producing sound.
Flute:
The flute is a wind instrument. When air is blown into the flute, the air column inside the instrument vibrates, creating the sound.