The belaklavion, sometimes just called the klavion, was a Bajoran musical instrument that was apparently quite difficult to master.

Both Ro Laren's father and Macias were known to play the instrument. Macias mentioned that though he had difficulties playing the klavion, he enjoyed the challenge.

When Ro Laren was very young and afraid of monsters under her bed, her father would play for her. He told her that the sound of the klavion had special powers, that monsters were afraid of it, and they'd disappear whenever they heard it. When she listened to the music as a child, she would never be afraid to sleep. (TNG: "Preemptive Strike")