This is a metronome (obviously). Besides setting a steady beat that helps me to play my violin in tempo, it also has a setting that plays the note A which allows me to tune my instrument. I never realized this before, but on the dial, right below where it says "A", it says 440 Hz, the frequency of the note A (!!!). This past week of physics has also made me realize why tightening the tuning pegs on my violin increases the pitch of the string. The wave speed of the string increases with the increase in tension. By winding the string around the tuning peg, I am increasing the tension of the string and increasing its wave speed. Increasing the wave speed of the string also increases its frequency. This higher frequency is picked up by my ear as a higher pitch.