Two tuning forks on individual resonance boxes for demonstrating the production of beat frequencies. It consists of two nickel plated tuning forks frequency 256Hz mounted on individual boxes. One tuning fork is provided with adjustable mass for varying frequency from normal frequency 256Hz. When both forks are set into vibration and brought close to each other from open end of boxes, an audible beat is produced. The rate of beat depends upon the frequency between forks.