Chorus waves are commonly observed and play a key role in regulating electron flux in Earth’s radiation belts. These waves often show rising or falling frequencies over time, known as rising-tone and falling-tone chorus. While rising-tone chorus has been widely studied, the origin of falling-tone chorus remains poorly understood. In this study, we analyze data from the Van Allen Probes and find that rising-tone chorus is typically generated upstream of the magnetic equator, whereas falling-tone chorus appears downstream. Using particle-in-cell simulations, we successfully reproduce falling-tone chorus waves and show that their generation is driven by nonlinear interactions between waves and energetic electrons. This work provides new insight into the nonlinear particle dynamics associated with chorus waves.