Why does a recorder make a lower pitch when more holes are covered?

A recorder produces a lower pitch when more holes are covered because covering holes reduces the effective length of the vibrating air column inside the instrument. When fewer holes are open, the air column is shorter, resulting in higher frequencies and pitches. Conversely, covering more holes lengthens the air column, which lowers the frequency and produces a deeper sound. This relationship between the length of the air column and pitch is a fundamental principle of wind instruments.