Why do tuning forks produce a clear tone with very few overtones?

A tuning fork produces a nearly pure tone with very few overtones because its design and physical properties favor a specific, stable vibration pattern that minimizes the presence of complex harmonic or nonharmonic frequencies.1

In the study of acoustics, a simple tone consists of only one frequency, whereas a complex tone is composed of a fundamental tone accompanied by various overtones. While many musical instruments produce rich timbre through the interaction of multiple harmonics, the tuning fork is engineered to isolate a single frequency. Because it vibrates in a way that approximates simple harmonic motion, it avoids the complex superposition of frequencies found in more intricate vibrating systems like strings or membranes. This characteristic makes the tuning fork an essential tool for the experimental study of sound and for establishing a standard pitch.23145